HYGIENE AS SCIENCE. MICROCLIMATE. PLACE AND VALUE OF HYGIENE IN THE SYSTEM OF MEDICAL SCIENCES AND nPRACTICAL ACTIVITY OF DOCTORS. METHODS OF HYGIENICAL nRESEARCHES. ORGANIZATION OF EDUCATIONAL-RESEARCH WORK nOF STUDENTS. STRUCTURE OF SES, SANITARY LEGISLATION.
A METHOD OF DETERMINATION AND HYGIENICAL ESTIMATION OF TEMPERATURE, nHUMIDITY, RATE OF MOVEMENT OF AIR, THEIR INFLUENCE ON A HEAT EXCHANGE. A nHYGIENICAL ESTIMATION OF THE COMPLEX INFLUENCING OF PARAMETERS OF MICROCLIMATE ON nTHE HEAT EXCHANGE OF MAN (KATATHERMOMETER, EQUIVALENTLY EFFECTIVE, RESULTING nTEMPERATURES).
1. HYGIENE AS SCIENSE
Health – nis defined as a state of ncomplete physical, mental and social nwell-being and not merely absence nof disease or infirmity.
Health is the functional nand/or metabolic efficiency of an organism, at any moment in time, at both the ncellular and global levels. All individual organisms, from the simplest to the nmost complex, vary between optimum health and zero health (dead).
Perfect health is an abstraction, which may not nbe attainable but is essential for an individual or a family or a group nor a community’s strivings. Optimum Health is the highest level of health nattainable by an individual in his/her ecological settings. Positive health nmeans striving for preservation and improvement of health. Negative health nmeans scientific efforts for prevention and cure of diseases. To promote and nmaintain a state of positive health an individual needs the following nprerequisites:
·Supply of fresh air and sunlight
· Safe and potable water supply
· Balanced diet
· Healthful shelter
·Adequate clothing hygienic nenvironmental sanitation
·Protection from communicable and nother avoidable afflictions
·Complete sense of protection and nsecurity both socially and economically
·A congenial social and cultural natmosphere.
· In additioan individual should have a regulated way of life with proper rest and nrelaxation and good and simple habits.
All these factors help to maintain a normal nbalance of body and mind, which is must for positive health. The study of all nthese factors constitutes a branch of medicine designated as preventive and nsocial medicine. Any imbalance or deviation in the above factors is likely to ncause a state of illness, when curative aspect of medicine comes into picture.
Hygiene n- is a basic preventive science imedicine. It generalizes all dates of theoretical and clinical disciplines ithe field of prophylaxis, integrates knowledge’s about complex influence of aenvironment for health of the man, work out principles and systems of npreventive measures.
The word Hygiene is derived from the Greek word (Hygeia) Hygieia — nthe goddess of nhealth.
IGreek nmythology, Hygieia (Roman nequivalent: Salus) was a daughter of Asclepius. nShe was the goddess of health, cleanliness and sanitation (and later: the nmoon), and played an important part in her father’s cult (see also: asklepieion). While her father was more directly nassociated with healing, she was associated with the prevention of sickness and nthe continuation of good health.
Hygiene nis defined as the science and art of preserving and improving health. Hygiene ndeals both with an individual and a community as a whole. Personal Hygiene is nthe term used for improvement of hygiene of an individual or a person. Social nHygiene is usually the term used for dealing with problems of sex especially nfor control of venereal diseases. Similarly other terms like mess hygiene, milk nhygiene, hygiene of feeding, hygiene of clothes, hygiene of infant feeding etc., are self-explanatory
Hygiene nand Good Habits are commonly nunderstood as preventing infection through cleanliness. nIn broader call, scientific terms hygiene is the maintenance of health and nhealthy living. Hygiene ranges from personal hygiene, through domestic up to occupational hygiene and public health; nand involves healthy diet, cleanliness, and mental health.
PREVENTIVE MEDICINE
“Prevention is better than cure” is an old nsaying. Preventive medicine deals with the measures to protect the individuals nfrom the diseases, and to keep them in a state of positive health. For this we nhave to ensure all the above-mentioned prerequisites required for the nmaintenance of positive health. The environments must be hygienic, with supply nof fresh air, safe potable water and balanced diet. This aspect of preventive nmedicine started gaining more importance from 18th century onwards nwith the discovery of various vaccines and sera for the protection against nvarious diseases like small pox, cholera, plague, whooping cough, tetanus, ntuberculosis, poliomyelitis etc
Ecology is nconstituted by the total environment of man. The environment of modern man is npartly natural and partly man-made. It consists of physical, mental and social nfactors, which are dynamic and interacting both within themselves and with the nlife process in the internal environment of men. The important physical nfactors are air, water, food, buildings, their contents and multiple devices nproduced by man to adjust the physical environment around him. The important nbiological factors are pathogens, other microorganisms as well as living nbeings, vectors, plants, etc., which have implications on health and disease. nThe important social factors are customs, beliefs, laws, peculiarities and nmodes of living of human beings with their implications on health and disease.
What nis pollution.htm
Environmental Sanitation
The word Sanitatio- is derived from the Latin word Sanitas which means a state of health. nEnvironmental Sanitation means the control of all those factors in man’s nsurroundings, which cause or may cause adverse effects on his health. The nsanitarian directs his efforts towards hygiene of water and food supply, nhygienic disposal of human wastes, hygiene of housing and control of vectors nand rodents etc.
The following definition now is accepted: «Hygiene nis a science, which investigates regularities of influence of the nenvironment on the organism of nthe man and npublic health with the purpose nof the substantiation nof the hygienic nnorms, sanitarian rules and measures, nrealization of which will ensure noptimum conditions for vital activity, nimproving of health and preventing nof diseases ».
The principal topics of nthe subject are:
· Hygiene of atmospheric nair
· Water supply hygiene
· Hygiene of nutrition
· Occupational hygiene
· Radiological hygiene
· Hygiene of children and teenagers
· Hospital hygiene
· Hygiene of extraordinary nsituation
· Tropical hygiene
Hygiene is a science of npreserving and promoting the health of both the individual and the community.
It has many aspects:
Ø npersonal hygiene (proper living habits, cleanliness of body and nclothing, healthful diet, a balanced regimen of rest and exercise);
Ø n domestic hygiene (sanitary npreparation of food, cleanliness, and ventilation of the home);
Ø npublic hygiene (supervision of water and food supply, containment nof communicable disease, disposal of garbage and sewage, control of air and nwater pollution);
Ø n industrial hygiene (measures that nminimize occupational disease and accident);
Ø mental hygiene (recognition of mental and emotional factors in healthful living) and so non.
2. THE AIM AND TASKS OF nHYGIENE
Basic aim of hygiene
Preservatioand improving the health of the man is a basic aim of hygiene.
Ithis occasion the English scientist E.Parce has told, nthat the hygiene has a great and generous purpose: «…To make development of nthe man most perfect, life most intense, wasting least fast, and death most nremote».
The tasks of a hygienic science:
1. Study of the natural and nanthropogenesis factors of the environment and social conditions which influence non health of the man.
2. Study regularities of ninfluence the factors and conditions of an environment on an organism of the nman or population.
3. Scientific substantiatioand working out of the hygienic norms, rules and measures, which help use nmaximum positively influencing on an organism of the man the factors of aenvironment and elimination or restriction up to safe levels unfavourable noperating ones.
4. Introduction in practice of npublic health services and national economy developed hygienic recommendations, nrules and norms check of their effectiveness and perfecting.
5. Prediction of the sanitarian situatiofor the nearest and remote perspective in view of plans of development of the nnational economy. Definition of appropriate hygienic nproblems, which implying from prognostic situation and scientific working out nthese problems.
3. BASIC METHODS OF HYGIENIC RESEARCHES
During the development the hygiene used many nmethods of study an environment and its influence on the health of the population. n
Methods nof hygiene
1. Methods of nenvironment studying.
2. Methods of nstudying of environmental influence on human organism and health
1. Methods of environment studying
Methods of sanitary examination with further sanitary ndescription
Speaking nabout methods of the research the exterior factors, first of all it is nnecessary point at method sanitarian description, which for a long time being nalmost only. It did not lost the value and now.
Specific nhygienic method is method of sanitary examination and describing which nis used for studying the environment.
Sanitary examination and describing is carried nout according to special programs (schemes), which contain questions. Answers nto these questions characterize the object, which is being examined nhygienically. As a rule it is usually supplemented by laboratory analyses n(chemical, physical, microbiological and other), which allows characterizing nenvironment from the qualitative side.
Instrumental and laboratory methods With the help of physical methods we can study microclimatic nconditions, electrical conditions of air, all aspects of radiant energy, nmechanical and electromagnetic oscillation, carry out the spectroscopic nanalysis and much other.
By chemical methods we cadetermine peculiarities of a natural structure of all elements of aenvironment, the quantitative and qualitative indexes of it contamination, nenable to make conclusion about sanitarian troubles of the investigated object.
The biological methods, first of all nbacteriological researches, for example, definition of a credit of the Esherichia colli, have much value nfor conclusion about epidemiological safety of the potable water.
Methods of Studying of Environmental Influence on HumaOrganism and Health
1. Methods of experimental investigation
A study response of an organism non various exterior actions plays the major nrole for development of modern hygiene. The experiment on the warm-blooded nanimals now is leading for nall its areas. nSo, toxico-hygienic researches nare compulsory for evaluation of toxicity of npoisonous substances, which uses in nindustry and agriculture. Not less widely there nare uses in municipal hygiene nfor analysis of industrial wastewater, nin hygiene of foods — for nthe definition of harmful impurities, nand in other nareas of hygiene. The skilful nrealisation of these researches allows receiving dates for development nof the appropriate nhygienic norms, methods of early ndiagnostics of professional diseases and for evaluation nof effectiveness preventive measures.
2. Methods of natural observation
Much value is represented by clinical observations of the people, nwhich are exposed of the defined exterior factors. In particular, defined value nhas working out materials of periodic medical examinations of working harmful ntrades. Comparing these observations with dates of the research of aindustrial medium, it is possible form a correct estimate of the recommended nhygienic norms.
Also, in hygiene is widely napplied the method of a sanitary – statistical analysis, with the help nof which may form a true notion about positive and negative influence on health nof the population: it physical development, morbidity, mortality, average life nexpectancy etc.
There nare widely used different kinds of hygienic experiments:
1 Experiment nwith simulation of natural conditions. They are used for examining and predicting processes which are going oin the surrounding world (for example, for examining, the influence of chemical nadmixtures on the processes of self-clearing of water in reservoirs).
2. Laboratory nexperiment on animals. It helps to nstudy influence of factors of environment on the organism which meets the goal nto substantiate hygienic norms. In the process of this experiment the following nmethods are used: physiological, biochemical, immunological, nhistological, microscopic, radiobiological, genetic nand others.
3. Chamber nexperiment on people. It is used nto study the influence of some factors on the human organism and determine the nnorms. This method is used to study such factors as microclimate, illumination, nnoise, neural-psychic strain, etc.
”Natural experiment” which helps to study influence of factors of nenvironment on the human health in real conditions of the life For example, nstudying health of people (especially children) who live at different distance nfrom enterprises throwing out into the atmosphere toxic gaseous substances. nNatural experiment allows to check-up hygienic norms nwhich were determined in the experiment on animals.
The nhealth of individuals is studied by way of medical examinations with the usage nof anthropometric, clinical, physiological, biochemical, immunobiological, roentgenological nand other methods of examinations. Their participation in labour and other ntypes of activity must be taking into account.
The nhealth of a certain group of people or of all population of the populated area n(region, republic, etc.) is studied with the help of sanitary – statistic nmethod. There are different criteria which characterize physical development, ndemographical peculiarities (birth-rate, death-rate, average life span and nothers), morbidity and pathology of studied group.
Epidemiological nmethod is close to sanitary – statistic method. It is used for studying of nspreading of this or that disease (hypertension, coronary disease, diabetes, nulcerous disease, etc.). They are studied during certain period (during. a nyear, month), on the certain territory (different regions of the city, nrepublic), among different groups of population (which differ one from another nby age, gender, occupation, conditions of water and food supply, conditions of nlife and others). Analysis of these data is used for determining of causes and nconditions which favor the development of disease, nfor liquidation of disease as regional pathology, for planning prophylactic nmeasures.
Methods of mathematical nstatistics and modelling are widely used.
Hygienic standardization:
Environmental nstandards are definite ranges of environmental factors, which are optimal, or nthe least dangerous for human life and health. In Ukraine basic objects of hygienic nstandardization are:
§ nMAC – maximum admissible nconcentration (for chemical admixtures, dust and other hazards)
§ nMAL – maximum admissible nlevel (for physical factors)
§ nLD – dose limit (for nionizing radiation)
§ nOptimum and admissible parameters of microclimate, lighting, solar radiation, atmospheric pressure and nother natural environmental factors.
§ nOptimum and admissible daily requirements in food and water.
Let’s study the methodical nscheme of hygienic norms of substantiation using, the example of MAC for some ntoxic substance. The first stage is stud physical and chemical nproperties of the substance, elaboration of methods of quantitative ndetermination of this substance in different subjects, determination of its nregimen of action on the human (duration, interruption, changes of intensity), nways of getting into the organism, study migration in different elements of the nsurrounding, mathematical prediction of duration of existence in different nsurroundings.
The second nstage is study direct influence on the organism. It is nstarted from ‘sharp’ experiments the main goal of which is getting initial toxicometric data about the substance (determination of LD50, nor LC50 threshold of strong action (LIMac) nand other. With the knowledge of physical and chemical properties of t he substance, its initial toxicological characteristics nand approximate level of MAC can be calculated. The third stage – nis conduction of ‘subsharp‘ experiment during l-2 nmonths for determination of cumulating coefficient and the most vulnerable nphysiologic systems and organs specification of mechanisms of action and nmetabolism.
The fourth n(basic) stage is carrying out chronic experiment which lasts n4-6 months in the case of modeling of working nconditions, 8-12 – communal conditions, 24-36 – in study processes of aging or ninduction of tumours.
During the experiment integral parameters are nstudied. They reflect condition of animals, degree of strain of regulative nsystems, functions and structure of organs which take part in processes of nmetabolism (activity of enzymes), influence of functional loadings.
Numbers of MACs of toxic chemical substances ithe Ukraine are various: for the air of working: zone – more than 800, water- n700, atmosphere air- 200, food-stuffs – more than 200, soil – more than 30.
Basic objects, which nare under the hygienic norms setting, can be divided into two groups.
The first group contains factors of anthropogenous origin, nwhich are unfavorable for human being, and are not nnecessary for the normal life activity (dust, noise, vibration, ionizing nradiation, etc.). MAC, MAL and LD are those parameters, which are set for this ngroup of factors.
The second group contains factors of natural surrounding which are nnecessary (in certain amount) for normal life activity (food-stuffs, solar nradiation, microclimatic factors and others). For this group the following nparameters must be set: optimum, minimum and maximum admissible parameters.
In those cases when factors influence on the humanot only directly (physiologically) but also indirectly (through the environment) nall types of possible influence must be examined at hygienic norms nsetting. For example setting of hygienic norms for toxic substance in the water nof natural reservoirs determination of maximum concentrations must be based oworsening of organoleptic properties of the water (organoleptic sign), toxic ninfluence (sanitary – toxicological sign) and disturbance of processes of nself-clearing of reservoirs (general sanitary sign). In this case MAC are set naccording that harmful parameter which is characterized by the lowest level of nconcentration Such parameter is called limiting.
THE nMETHOD OF DETERMINATION AND HYGIENIC ESTIMATION OF AIR TEMPERATURE AND nATMOSPHERIC PRESSURE
Air ntemperature is a measure of how hot or cold the air is. It is the most commonly nmeasured weather parameter. More specifically, temperature describes the nkinetic energy, or energy of motion, of the gases that make up air. As gas nmolecules move more quickly, air temperature increases.
Why nis Air Temperature Important?
Air temperature affects the growth and reproduction of plants and nanimals, with warmer temperatures promoting biological growth. Air temperature nalso affects nearly all other weather parameters. For instance, air temperature naffects:
- the rate of evaporation
- relative humidity
- wind speed and direction
- precipitation patterns and types, such as whether it will rain, snow, or sleet.
n
How is nAir Temperature measured?
Temperature nis usually expressed in degrees Fahrenheit or Celsius. 0 degrees Celcius is equal to 32 degrees Fahrenheit. Room temperature nis typically considered 25 degrees Celcius, which is nequal to 77 degrees Fahrenheit.
A nmore scientific way to describe temperature is in the standard international nunit Kelvin. 0 degrees Kelvin is called absolute zero. It is the coldest ntemperature possible, and is the point at which all molecular motion stops. It nis approximately equal to -273 degrees Celcius and n-460 degrees Fahrenheit.
TEMPERATURE nSCALES
Temperature is a physical quantity that is a measure of nhotness and coldness on a numerical scale. It nis a measure of the local thermal energy of matter or radiation; it is measured by a thermometer, which may becalibrated
in any of various temperature scales, nCelsius, Fahrenheit, Kelvin, etc., etc.
Much nof the world uses the Celsius scale n(°C) for most temperature measurements. It has the same incremental scaling as nthe Kelvin scale nused by scientists, but fixes its null point, at0°C = 273.15K, napproximately the freezing point of water (at one atmosphere of pressure).[note 1] The nUnited States uses the Fahrenheit scale nfor common purposes, a scale on which water freezes at 32 °F and boils at n212 °F (at one atmosphere of pressure).
For npractical purposes of scientific temperature measurement, the International System nof Units (SI) defines a scale and unit for the nthermodynamic temperature by using the easily reproducible temperature of the triple point of nwater as a second reference point. The reason for this choice is that, unlike nthe freezing and boiling point temperatures, the temperature at the triple npoint is independent of pressure (since the triple point is a fixed point on a ntwo-dimensional plot of pressure vs. temperature). For historical reasons, the ntriple point temperature of water is fixed at 273.16 units of the measurement nincrement, which has beeamed the kelvin in honor of the Scottish physicist nwho first defined the scale. The unit symbol of the kelvin is K.
Absolute nzero is defined as a temperature of precisely 0 kelvins, nwhich is equal to −273.15 °C or −459.67 °F.
One nof the earliest temperature scales was devised by the German physicist Gabriel Daniel Fahrenheit. According nto this scale, at standard atmospheric pressure, the freezing point (and nmelting point of ice) is 32° F, and the boiling point is 212° F. The centigrade, or Celsius scale, ninvented by the Swedish astronomer Anders Celsius, and used throughout most of nthe world, assigns a value of 0° C to the freezing point and 100° C to the nboiling point.
http://www.ux1.eiu.edu/~cfadd/1360/19Temp/Absolute.html
Iscientific work, the absolute or Kelviscale, invented by the British mathematician and physicist William nThomson, 1st Baron Kelvin, is used. In this scale, absolute zero is at -273.16° nC, which is zero K, and the degree intervals are identical to those measured othe Celsius scale. The corresponding “absolute nFahrenheit” or Rankine scale, devised by the nBritish engineer and physicist William J. M. Rankine, nplaces absolute zero at -459.69° F, which is 0° R, and the freezing point at n491.69° R. A more consistent scientific temperature scale, based on the Kelviscale, was adopted in 1933.
Aabsolute temperature scale invented in the 1800’s by William Thompson, Lord nKelvin. It places the zero point of the scale at absolute zero, nthe temperature which scientists believe is the lowest possible. All molecular nmotion would stop there. A Kelvin degree is the same size as a Celsius degree, nso the two scales simply have a constant offset.
Temperature.
Ainstrument called thermometer ascertains this. n
Generally mercury or nalcohol is used in the thermometers. Mercury is used in thermometers meant for recording high temperatures on account of its uniformity in expansion at different ntemperatures, easy visibility, high boiling point and low vapor pressure. Alcohol is used in thermometers for recording low temperatures, because it does not freeze even at low temperatures. Several nkinds of thermometers are used
These are:
(1)Standard nor Dry Bulb Thermometer. It is an ordinary nthermometer.
(2)Maximum nThermometer. It is used for registering the highest temperature attained in the day or any other period. The thermometer nis laid in a horizontal nposition. In the stem of the thermometer, part nof the mercury column is separated by air. When the temperature rises the mercury expands and pushes this broken column forward. nBut this column does nnot recede when the temperature falls and the maimercury column contracts. The reading taken indicates the maximum temperature attained during the day.
(3) nThe Minimum Thermometer. It is used for recording the lowest ntemperature during the night or during the early hours of morning. A small glass index is enclosed in the spirit, which fills the bulb and a part of the stem. When setting the instrument, the index is first brought to the top of the column of the spirit and the instrument is placed in a horizontal position. When the temperature rises, the spirit expands and flows past the index, but when the temperature falls, the spirit contracts and carries the index along with it. The lowest temperature is thus registered. The instrument can be readjusted by tilting.
(4) Six’s Maximum and Minimum Thermometer. It is a combination of maximum and minimum thermometers and gives a double reading. It is however, not a very accurate instrument and is therefore no more being used now nin Indian Meteorological nobservatories.
Methods nof temperature measure
Ovalue of temperature regime on the room measure do in difference place on a nvertical.
First measure of temperature is done on 10 cm from the nfloor and characterizes air on foot level.
Second measure do on 1,5 meter from the nfloor – in respiration zone of man.
Third nplace is on 50 cm from ceiling and characterizes convection ithe room. In hospital the second place is situated on level of bad. Measuring nof temperature in horizontal line is done in three points: from external angle nto internal angle on 20 cm. Change of temperature in time is measured by nthermograph. It’s done in three places on 1,5 cm from the floor.
Thermometer
It nis instrument used to measure temperature. The invention of the thermometer is attributed nto Galileo, although the sealed thermometer did not come into existence until nabout 1650. The modern alcohol and mercury thermometers were invented by the nGerman physicist Gabriel Fahrenheit, who also proposed the first widely adopted ntemperature scale, named after him.
Types nof thermometers
•Wide nvariety of devices are employed as thermometers. The nprimary requirement is that one easily measured property, such as the length of nthe mercury column, should change markedly and predictably with changes itemperature.
•Electrical nresistance of conductors and semiconductors increases with an increase in temperature. For thermistor of givecomposition, the measurement of specific temperature will induce specific nresistance. This resistance can be measured by galvanometer and becomes measure nof the temperature. With proper circuitry, the current reading can be converted nto a direct digital display of the temperature.
Very naccurate temperature measurements can be made with thermocouples in which small voltage difference (measured imillivolts) arises when two wires of dissimilar metals are joined to form a nloop, and the two junctions have different temperatures.
•Optical npyrometer is used to measure ntemperatures of solid objects at temperatures above 700° C (about 1300° F) nwhere most other thermometers would melt. At such high temperatures, solid nobjects make so-called glow color phenomenon. The color at which hot objects nglow changes from dull red through yellow to nearly white at about 1300° C n(about 2400° F). The pyrometer contains a light bulb type of filament ncontrolled by a rheostat (dimmer switch) that is calibrated so that the colors nat which the filament glows corresponding to specific temperatures.
•Another ntemperature-measuring device, used mainly in thermostats, relies on the differential thermal expansion betweetwo strips or disks made of different metals and either joined at the ends or nbonded together.
Special ntypes of thermometers
Thermometers nmay also be designed to register the maximum or minimum temperature attained.
•Maximum nthermometers.A mercury-in-glass clinical thermometer, for example, is maximum-reading ninstrument in which trap in the capillary tube between the bulb and the bottom nof the capillary permits the mercury to expand with increasing temperature, but nprevents it from flowing back unless it is forced back by vigorous shaking.
•Minimum nthermometers. Inside capillary tube is alcohol with glass npin. When temperature increase ethanol moves pin. When temperature decrease nethanol paces pin for a minimal temperature.
Thermograph.
•Thermograph nconsists of vertical pen, bimetallic laminas and clack mechanism. Perceiving npart of instrument is bimetallic laminas, which change it curvature by change nof temperature. By means system of levers which passes changing curvature of nbimetallic laminas by righting pen and we have graphical illustration of ntemperatures on paper of clack mechanism.
Table nof Equivalent Temperatures by Celsius and Fahrenheit scales
C n= (F – 32) х 100/180;
F n= (C х 180/100) + 32.
Measuring nMaximum and Minimum temperature
If npossible it is best to record the daily maximum and minimum temperature as well nas that which you record at a specific moment in time when you make your nobservations. You can simply use your normal thermometer. With this you need to nrecord temperatures at about 14:00 where the daily maximum usually occurs, or nvery early morning when the temperature is similar to the overnight minimum. nThese are good times to take your am/pm measurements.
Studying nthe temperature condition of the indoor air
The ntemperature is measured in 6 or nmore points to fully characterize the temperature conditions of premises.
Thermometers n(mercurial, alcohol, electric or psychrometer dry nthermometers) are placed onto nsupport racks at three points 0.2 meter high above the floor, at nthree points 1.5 meters high (points t2, t4, t6 and t1, t3, t5 respectively) nand at 20 cm from the wall along the diagonal section of the laboratory naccording to the diagram:
The nthermometer data are fixed after 10 minutes of the exposition at the point of nmeasurement.
The nair temperature parameters in premises are calculated using following formulas:
а) nthe average temperature in the npremises:
а) ntaver.= ,
b) the nvertical variation of the air temperature:
D n n
c) the nhorizontal variation of the air temperature:
D n n
Diagrams nand calculations are written down into the protocol, the hygienic assessment is made. It is necessary to consider the nfollowing data: the optimal nair temperature must be from +18 to +21оС in residential nand class–room premises, wards for somatic patients, the vertical temperature nvariation must be no more than 1.5-2.0оС, horizontal – no more than 2.0-3.0оС. The ndaily temperature variations are determined using the thermogram, prepared ilaboratory using the thermograph. The daily temperature variation must be no nmore than 6оС.
The nallowable and optimal standards of the temperature, presented in the table 1 are the hygienic assessment ncriteria for residential and public premises.
Table n1
The ntemperature standards for residential, public and administrative premises
Comment:
* the allowable temperature is no more than 28оС for public and nadministrative premises, which are permanently inhabited, for regions with the estimated outdoor air ntemperature of 25оС and above – no more than 33оС.
** the allowable temperature is 14оС nfor npublic and administrative premises where the inhabitants are wearing their nstreet clothes.
The nstandards were established for people that are continuously staying in the npremises for 2 hours or more.
The ntemperature standards for the workplace air of industrial areas are set in the nState Standard #12.1.005-88 “General nsanitary and hygienic requirements to the workplace air”, depending on the season (cold, warm) and work category (easy, moderate and hard).
The noptimal temperature standards for the cold season are set from 21 to 24оС during the physically easy work and from 16 to 19оС during the physically hard nwork. These temperature ranges correspond to 22-25оС and n18-22оС during the warm season. The allowable maximum ntemperature is no more than 30оС nfor the warm season, the allowable minimum temperature for the cold nseason is 13оС.
Thermoregulation is nthe ability of an organism to keep its body ntemperature within certain boundaries, even when the nsurrounding temperature is very different. nThis process is one aspect nof homeostasis: na dynamic state of stability between nan animal’s internal environment and its external environment (the study of nsuch processes in zoology has been ncalled ecophysiology or physiological necology). If the body is nunable to maintain a normal ntemperature and it increases significantly nabove normal, a condition known as hyperthermia occurs. For nhumans, this occurs when the nbody is exposed nto constant temperatures of approximately 55 n°C (131 °F), and any prolonged nexposure (longer than a few hours) nat this temperature nand up to naround 75 n°C (167 °F) death is almost inevitable. Humans may also nexperience lethal hyperthermia when the wet nbulb temperature is sustained above 35 °C (95 °F) for six nhours. The nopposite condition, when body temperature ndecreases below normal levels, is known as hypothermia.
The nradiant temperature and the wall temperature determination
The nspherical thermometers are used for the radiant temperature determination ipremises, wall thermometers – for the wall temperature determination (see fig. 6.1 а, b)
The nspherical thermometer consists of the thermometer located inside the hollow nsphere 10-15 cm in diameter nand covered with porous polyurethane foam layer. This material has similar ncoefficients of the infrared radiation adsorption as the human skin.
The nradiant temperature is also determined at 0.2 and 1.5 meters above the floor.
The ndevice has the considerable inertia (up to 15 min.), that is why the thermometer ndata must be takeo earlier than after that time.
The nspherical thermometer data at the height of 0.2 and 1.5 m must not vary by more nthat 3оС icomfortable microclimate conditions.
Fig. 6.1. Thermometers for the radiant ntemperature determination
a – the section of the spherical nblack thermometer
(1 n– 15 cm diameter sphere ncovered with dull black paint; 2 n– thermometer with the nreservoir at the center of the sphere)
b – Wall thermometer with the flat turbinal reservoir n
(1 n– thermometer; 2 – base cover (foam-rubber); 3 –sticky ntape)
The nvalues of the radiant temperature below are recommended for different premises (see table 2).
Table n2
Standard nvalues of radiant temperature for different premises
Special nthermometers with the flat turbinal reservoir are used for the wall temperature ndetermination. These thermometers are attached to the wall with special putty (wax with colophony addition) or alabaster. The wall temperature is also determined nat 0.2 and 1.5 meters above the floor. In some cases it is necessary to ndetermine the temperature of coldest parts of the wall.
The nhigh levels of infrared irradiation in especially hot manufacture areas are nmeasured using actinometers (solar radiatioinstrument) and are expressed in mcal/(сm2×min).
Water nvapor
The nperson during all life is exposed to water vapor. Its quantity in air npermanently changes: it decreases or increases. When in air a lot of water nvapor is stored, the conditions for evaporation of moisture are worse. In air nsuch quantity of water vapor can be stored, that it resilience equals nresilience of liquid that evaporates, – and then the evaporation ceases.
The nevaporation depends on temperature of air, the above last, the implements nevaporation fan-in harder. There fore evaporation as nthough goes after temperature of air; temperature of air – is increased the nevaporation is increased also; temperature of air is lowered, the evaporatiois lowered also.
Air nhumidity
Humidity is moisture content of the atmosphere. The natmosphere always contains some moisture in water vapor; nthe maximum amount depends on the temperature. The amount of vapor that will saturate the air increases with temperature nrise. At 4.4° C (40° F), 454 nkg (1000 lb) of moist air contain maximum 2 kg of nwater vapor; at 37.8° C (100° F), the same amount of nmoist air contains maximum 18 kg of water vapor. Whethe atmosphere is saturated with water, the level of discomfort is high because nthe evaporation of perspiration, with its attendant cooling effect, is nimpossible.
Humidity is specified in several different ways. nThe weight of water vapor contained in a volume of nair is known as the absolute humidity and is expressed in grams of water vapor per ncubic meter.Relative nhumidity, given in weather forecasts, is the ratio between the actual content nof the air vapor and the content of the air vapor at the nsame temperature saturated with water vapor.
The nmaximum damp is measured by that quantity of a water pair in grammas, which one saturates completely 1m3 of air at givetemperature
The nrelative humidity is an attitude of absolute humidity to maximum at givetemperature, expresses in percentage, that is:
R=A n/ F х 100,
Where nR – relative humidity;
•A- nabsolute humidity;
•F n- maxime humidity.
The nrelative humidity interests us because its characterize saturation of air by a pair, its ndryness. For example, if we speak, that relative humidity 60 %, from this nnumber it is visible, that 40 % of a moisture does not nsuffice to saturation of air, that is, it has a capability to receive a nmoisture. At relative humidity 80 % we could say, that in this case elasticity nof a pair in atmosphere is higher, at her the liquid evaporates worse. At 90 % n- it is even worse.
Knowing absolute humidity it is possible to ndefinite dew point, that is that temperature, at which one the absolute nhumidity becomes maximum and the air humidity will begin to be condensate and nto precipitate by the way of drops of water. Let’s consider such example. What nthe temperature this damp will begin to saturate air? It also means to find dew npoint.
The nair humidity can be described as deficit of saturation. The deficit of nsaturation is a difference between maximum and absolute humidity at same ntemperature. Together with it there is also concept a physiological deficit of nsaturation. It – difference between maximum damp at the temperature of bodies nof the person 36,5 degree and absolute humidity of nair.
The nmost commonly used measure of humidity is relative humidity. nRelative humidity can be simply defined as the amount of water in the air nrelative to the saturation amount the air can hold at a given temperature nmultiplied by 100. Air with a relative humidity of 50% contains a half of the nwater vapor it could hold at a particular temperature.
Figure n-1 illustrates the concept of relative nhumidity.
The nfollowing illustration describes how relative humidity changes in a parcel of nair with an increase in air temperature. At 10° Celsius, a parcel of dry air nweighing one kilogram can hold a maximum of 7.76 grams of water vapor
Physiological nrelative humidity
Hygiene nuses also concept of physiological relative humidity. It is attitude of nabsolute humidity at given temperature of air to maximum at 36,5 degree, expressed in percentage. Physiological relative nhumidity characterizes capability of air to accept damp that evaporates at body ntemperature. It enables more precisely to evaluate effect of moist air.
Air nhumidity can be described as deficit of saturation. The deficit of saturatiois difference between maximum and absolute humidity at same temperature.
There nis also a concept of physiological deficit of saturation. It is difference nbetween maximum damp at body temperature person 36,5 ndegree and absolute humidity of air. The physiological deficit of saturatiolets us define how many grams of water the person can spend by evaporation igiven conditions.
Air nhumidity is very relevant hygienic nfactor because it influences thermo exchange of the person. At low temperatures nin moist air the feeling of cold is stronger than in dry air at the same ntemperature.
It nis by outcome that the moist air has large heat conductivity and thermal ncapacity. From the same reason in wet clothes it is much more ncold: pores of tissues charged with moisture, and its well carries out nheat.
Humabody permanently loses moisture either by water vapor or by liquid water. It is nestablished that in quiet condition at room temperature the person loses by nskin approximately 20% of moisture, mild – 15 %, remaining part – urine and nfeces. Therefore, in these conditions approximately 35% of water is lost by nevaporation and 65% – in liquid with feces and urine. By activity and heat of nair – in the contrary: 60% of water is lost by evaporation from skin and mild nand much less by urine and feces.
Normal nrelative air humidity in dwelling apartments is 30-60%. A great range of normal nair humidity is explained fluctuations by the fact , nthat its influence on the organism depends on a number of conditions. In peace nwhen the air temperature is 16-200С with a light air motion the noptimum humidity will be 40 – 60%. During physical work when the air ntemperature is above 200С or below 150С air humidity must nnot be more than 30-40%, and when the temperature above 25 0С ndesirable to bring relative humidity down to 20%.
Air nhumidity determination methods
Humidity nis determined by psychrometes and hygrometers. Hygrographs ndetermine humidity fluctuations for a day or a week. Absolute air humidity is ndetermined by psychrometes (from greek psychros – cold).Psychrometes are of August and Assman ntypes.
August npsychrometer consists nof two nidentical mercury thermometers fixed on a support. By temperature difference odry and humid thermometers we can define absolute air humidity with a help of ntable or formula.
Assman psychrometer consists of ndry and humid thermometer situating in metal casing that protects from nradiation temperature. There is a ventilator in the upper part of the device. nVentilator is wound up and during 5 minutes in summer (15 minutes in winter) nregisters a temperature difference.
Relative nhumidity is measured by hygrometer. nIt consists of metal frame in the middle of which a fair defatted woman’s hair nis lightened. When humidity is low the hair becomes shorter, when it is high it nbecomes longer.
Instruments nto Measure Humidity
A nwhirling psychrometer is a type of hygrometer which can be whirled around like a nfootball rattle to take readings. You can directly read off the percentage nrelative humidity. It is a good idea to wrap it in a damp cloth for a while and nthen set the dial to read 100 %. Like paper, human hair stretches when moist nand shrinks when dry. Humidity recorders use this principle, and you can make a nsimple hygrometer using this method.
http://www.piercecollege.com/offices/weather/psychrometer.html
The nPsychrometer measures the wet and dry bulb temperature and under natural nevaporation conditions the state of a given mass of air can be described by its ntemperature and vapor pressure. If water is allowed to evaporate in an isolated nmass of unsaturated air , it latent heat content increases and its sensible nheat content decreases. The process will stop when the air becomes saturated at nthe wet bulb temperature ( Tw). The change in latent heat must equal the change nin sensible heat. http://weather.nmsu.edu/Teaching_Material/soil698/psych.html
A npair of thermometer placed parallel inside the screen with a bare bulb on the nright indicating the air temperature and is called dry bulb thermometer. nAnother thermometer on the left whose blackened globe is covered with a nmoistened muslin wick is called wet bulb thermometer. Since they are usually nusing in a pair, therefore, we normally call them psychrometer.
The nabsolute humidity is calculated using the Regnault nformula:
А n= f – a · (t n- t1) · nB,
where, А – the nair absolute humidity at the current temperature in Hg mm;
f – maximum pressure of water vapour nat the wet thermometer’s temperature (see the table of saturated water vapours, ntable 3);
nа – psychrometric coefficient is 0.0011 for enclosed spaces;
t – temperature of the dry thermometer;
t1 – temperature of the wet thermometer;
В – barometric pressure during the nhumidity determination, Hg mm.
The nrelative humidity is calculated using the following formula:
P n= ,
where, Р –the value of relative humidity to be found, %;
А – absolute humidity, Hg mm;
F – maximum pressure of nwater vapour at the dry thermometer temperature, Hg nmm (see the table of nsaturated water vapours, table 3).
Table n3
Maximum npressure of the air water vapour of premises
Psychrometric tables for nthe August psychrometer are used for the relative nhumidity (RH) determination (if the air velocity is 0.2 m/sec.). The value of RH is found at the npoint of the dry and wet thermometers data intersection, table 4.
The npsychrometer operation is based on the fact that the nrate of the water evaporation from the surface of dampened psychrometer’s reservoir is proportional to the air dryness. The drier the air – the lower is nthe wet thermometer’s result in comparison to the dry thermometer due to the nlatent evaporation.
Determinatioof the air humidity using the Assmann aspiration psychrometer
The nsignificant disadvantage nof August psychrometer is its dependence othe air velocity. The air nvelocity influences the evaporation intensity and the device’s wet thermometer ncooling.
This ndisadvantage has been eliminated in Assmann psychrometer due to the usage of the ventilator (see fig. 6.2-b). The ventilator produces the constant air nmovement at the 4 m/sec speed near thermometers’ reservoirs. As a result data ndoes not depend on the air velocity either inside or outside of the premises. nFurthermore, thermometers;’ nreservoirs of this psychrometer are protected with nreflecting cylinders around psychrometer’s reservoirs nfrom the radiant heat.
The ncambric of Assmann aspiration psychrometer nwet thermometer is dampened using the pipette, the spring of the aspiration devise is set or the psychrometer with electrical ventilator is plugged in. nAfter these procedures the psychrometer is hung up nonto the support at the determination point. The data of wet and dry thermometers nare taken 8-10 minutes later.
The nabsolute air humidity is calculated using the Sprung nformula:
,
where: А – absolute nair humidity in Hg mm;
t – maximum pressure of water vapour nat the wet thermometer temperature (see the table of saturated water vapours, ntable 3);
0.5 – constant psychometric coefficient;
t – temperature of the dry thermometer;
t1 – temperature of the wet thermometer;
В – barometric pressure at the determination moment in Hg mm.
Relative nhumidity is determined using the following formula:
,
where: Р –the nvalue of relative humidity to be found, %;
А – absolute humidity, Hg mm;
F – maximum humidity at the dry thermometer temperature, Hg mm (see table 3).
Relative nhumidity is determined using the psychrometric tables for naspiration psychrometers. The value of the relative humidity is nfound at the intersection point of the dry and wet thermometer data (see table 5).
Hair nor membrane hygrometers are used for the determination of the relative humidity nof the air. These devices measure the relative humidity directly. The nhygrometer operation is based on the facts, that the degreased hair lengthens, nand the membrane/diaphragm weakens when it’s damp, and vice-versa when they are ndry (see fig. 6.2-c).
Table n5
The nrelative humidity standards for residential, public and administrative premises n(abstract from Building Norms and Rules 2.04.05-86)
Note:* Allowable humidity is 75% for regions nwith the estimated outdoor air relative humidity more than 75%.
Standards nare set for people who continuously stay in premises for more than 2 hours.
Humidity deficit (the difference between the maximum and absolute air nhumidity) is determined using the table of saturated water vapours. The absolute air nhumidity, calculated using Regnault or Sprung nformulas is subtracted from the value of maximum air humidity according to the ndry psychrometer’s thermometer.
Physiological nhumidity deficit (the difference between the maximum air humidity at 36,5оС body temperature and absolute air humidity) is determined using the same table of saturated water nvapours (see table 3).
Dew npoint (temperature whethe absolute air humidity is maximum) is determined nusing the same table of saturated water vapours (see table 3) in reverse ndirection. The temperature when the absolute air humidity is equivalent to the maximum, is found nusing the value of absolute humidity.
The nscheme shows, that the rise of temperature provokes the maximum humidity nincrease in geometric progression, nthe absolute humidity – in arithmetical progression. When the air temperature rises, the nrelative humidity is decreases. As na result the amount of water in the air (absolute humidity) is nessentially lower in cold seasons than in summer, but is closely related to saturation (maximum humidity). That is why the relative humidity is nhigh in cold seasons and low in summer usually.
The ndaily temperature, the air humidity and the atmospheric pressure variation are ndetermined using the thermograph, hygrograph and barograph respectively
WHAT nIS DRY AIR?
There nare two ways in which dry air is referenced to in meteorology. Both of these ways are nexplained below:
1. nOne ndefinition of dry air is a theoretical sample of air that has no water vapor. When looking at tables in meteorology textbooks you nwill notice that for the composition of gases in the atmosphere there will noften be a table that shows the abundance of each major gas within dry air. nThis is done since water vapor is a variable gas n(ranging from a trace to around 4%). The amount of water vapor nin the air depends on the dewpoint of nthe air. When water vapor is ignored what is left is na fairly fixed percentage of the percent by volume or npercent by mass of Oxygen, Nitrogen and Argon. nHowever, air in the atmosphere will not be perfectly dry since even in very ncold air there will still be a trace of water vapor.
2. n Another definition of dry air is air that has na low relative humidity. nWhen the relative humidity drops below about 40% the air feels dry to skin. If nvery low relative humidities persist it can make the nskin dry, lips chapped and can put more static in the air. In the winter wheair with a low dewpoint from outside is heated and nbrought inside the air will decrease in relative humidity. To add moisture to nthe air some people will buy humidifiers. Although this air is referred to as ndry air it is not perfectly dry. In some cases air will be referred to as dry neven when the outside relative humidity is high but the dewpoint nis low. This is because even if the air has a high relative humidity of 90% noutside, once that air is brought inside and heated the relative humidity will ndecrease significantly. In situations in which the dewpoints nare low outside (less than around 32 F) that air will often be referred to as ndry by weather forecasters especially if the skies are clear.
The nrole of earth surface type in appearing of winds
Wind nis air in motion. It is caused by horizontal variations in air pressure. The ngreater the difference in air pressure between any two places at the same naltitude, the stronger the wind will be. The wind direction is the directiofrom which the wind is blowing. A north wind blows from the north and a south nwind blows from the south. The prevailing wind is the wind direction most ofteobserved during a given time period. Wind speed is the rate at which the air nmoves past a stationary object.
Measuring nof wind speed
Plenty nof instruments can measure wind.
•Wind nvane measures wind direction. Most nwind vanes consist of a long arrow with a tail that moves freely on a vertical nshaft. The arrow points into the wind and gives the wind direction.
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•
•Anemometers measure wind speed. Most anemometers nconsist of three or more cups that spin horizontally on a vertical post. The nrate at which the cups rotate is related to the speed of the wind. The cup of nanemometer has measuring borders from 1 to 50 m/sec, the wing one – from 0,5 to n15 m/sec.
•Cathathermometer n– alcohol thermometer with cylindrical or globular reservoir and a capillary ntube, dilated upwards, can measure air motion speed from 1,5 to 2 m/sec.
Anemometer –
•A ncup anemometer has metal cups which nrotate in the wind.
•A nswinging-arm anemometer records the nforce of the wind against a single ball or plate. With a ventimeter nwind blows into a hole at the bottom of a tube and raises a plate up it.
•A nDwyer wind meter similarly uses a nball. You can easily make a simple anemometer.
Usage of “wind rose” in preventive nsanitary control for settlements, industrial enterprises, resting-places nbuilding.
The ndirection of a wind is determined by that part of horizont nfrom where it blows. A direction and force of wind is taken into account for nneed of construction and planning of cities. As the direction of a wind is nconstantly changed, therefore it is necessary to know, what winds dominate ithis district. For this purpose all directions of winds on stretch of season or nyear are taken into account. On this data they create the schedule named n”rose of winds”. Thus, “rose of winds” represents a ngraphical image of recurrence of winds.
Wind nscale
Classification nof Wind Speed
Wind nspeed can be given according to the Beaufort Scale nmainly used to report weather at sea, “a force 9 gale” for example. nOn land, various indicators such as the movement of smoke or branches, nenable the wind speed to be estimated with reasonable accuracy.
•Force n1: 3 km/h (2 mph) smoke drifts
•Force n2: 9 km/h (5 mph) leaves rustle
•Force n3: 15 km/h (10 mph) flags flutter
•Force n4: 25 km/h (15 mph) small branches move
•Force n5: 35 km/h (21 mph) small trees sway
•Force n6: 45 km/h (28 mph) large branches move
•Force n7: 56 km/h (35 mph) whole trees sway
•Force n8: 68 km/h (43 mph) twigs break
•Force n9: 81 km/h (50 mph) branches break
•Force n10: 94 km/h (59 mph) trees blow down
•Force n11: 110 km/h (69 mph) serious damage
•Force n12: 118 km/h (74 mph) hurricane damage
Wind nProjects and Activities
There are lots of projects related nto wind speed and direction. You can build a lot of the instruments yourself n(look at things to do). Investigate why the wind does what it does!
Ienclosed spaces the running speed of air is determined in meters for one nsecond. The more air in a location varies, it is purer and health. But to admit nof high speeds of motion of air in a location it is impossible, as flows of ncold air, which one acts in a location, can derivate draughts. Is established, that the draught can call in the person or noffensive feels or sometimes catarrhal diseases. The feel of a draught nis at a running speed of air of 0,5m/sec and above.
•Therefore nat cooling locations it is undesirable to make motion of air with speed of n0,5m/sec and more, specially nin a cold season.
•The nmotion of air near to temperature and damp it influences heat output by aorganism and, means, on thermo exchange of the person.
•Let’s nconsider such example. Let’s allow, that temperature of air high, or is little nbit lower from temperature of a human body. The relative humidity is high also. nUnder such circumstances heat output by a body of the person becomes difficult, nas also temperature of air high. Close up to temperature of a human body. The nstay of the person in such conditions conducts to an overheating.
Atmospheric npressure
http://www.physicalgeography.net/fundamentals/7d.html
What nis Pressure?
Air nor atmospheric pressure, is the force exerted on the Earth, by the weight of nthe air above. That depends on how high the column of air is, so the higher the nsurface, the less the pressure. That is why you set your barometer to the nheight of your house or school above sea-level to get correct readings. Air npressure basically refers to the volume of air in a particular environment, nwith greater volumes creating higher pressures. On the earth’s surface, for nexample, it is known as “atmospheric pressure” and refers to the nweight of the earth’s atmosphere pressing down on everything. Changes ipressure can impact the temperature, weather patterns, and cause physiological nproblems for people and animals. This pressure can even impact the performance nof a basketball or similarly inflated object.
Atmospheric nPressure
On the earth, the average air pressure at sea nlevel is 1.03 kilograms per square centimeter n(kg/cm2) or 14.7 pounds per square inch (psi); this is commonly measured ibars, in which atmospheric pressure is about 1 bar. This means that hundreds of npounds of pressure are pressing on everyone from all sides, at all times. Humans and other animals are able to survive nthis pressure because their bodies evolved on the surface where it is nnatural. If the pressure increases or ndecreases, it can result in discomfort or even death.
Changes nin Pressure and Weather
Atmospheric npressure varies slightly over the earth’s surface, and variations in pressure nare responsible for various types of weather. nLow pressure systems are associated with storms, tornadoes, and hurricanes. Sometimes the air pressure at sea level cadrop as low as 870 millibars, which is about 85% of naverage air pressure. This only happens nduring the most severe storms. Pressure nvariations on the earth’s surface cause wind: as high pressure air moves toward nlow pressure areas, creating gusts.
Various nPressures at Different Altitudes
Othe top of Mt. Everest, the tallest mountain on earth, the air pressure is just nabout a third of what it is at sea level. Humans at high altitudes ofteexperience discomfort, such as ear popping, due to differences in their ninternal and external pressures. At 16 kilometers (km) or almost 10 miles above the surface, nslightly higher than the cruising altitude of a typical jet liner, pressure is nonly 1/10th what it is at sea level. nBecause low air pressure can be very unpleasant for humans, due to low noxygen content, all areas of aircraft that contain passengers are artificially npressurized. In the event of a rupture in an airplane’s fuselage, unsecured nitems may be “sucked” out of the craft as the high pressure air nwithin it rushes out into the low pressure environment outside.
Higher nAltitudes and Outer Space
At n31 km or about n19 miles above the earth’s surface, in the stratosphere, the air pressure is nonly 1/100th what it is at sea level. nFrom this level on, the atmosphere quickly deteriorates into nnothingness. Above 100 km or just over n62 miles above the surface, the international definition for outer space, the npressure approaches zero and nearly becomes a vacuum. Humans cannot exist nunprotected in such a low-pressure environment.
Why nis it Important?
Different npressure regimes have different types of weather associated with them.
Barometer nreadings are plotted on a pressure chart. Points on a map that have the same nair pressure are connected by lines known as isobars. By studying the patterns nshown by isobars, forecasters can make predictions about how the weather will ndevelop. We can identify “troughs” of low pressure and n”ridges” of high pressure.
Barometer
http://www.stuffintheair.com/barometermakes.html
Types nof barometers
Mercury nsiphon barometer nconsists of long vertical tube.Instrument contains nmercury. We get the result after summation of hailing mercury tube in long and nshort knee.
Mercury-cupping nbarometer consists of vertical glass tube which has mercury nsolder in upper part and open in lower part. Lower part is put into cup with nmercury.
Metal nbarometer aneroid. Maipart of this barometer is metal reservoir with cavity. When pressure changes, nchange volume and forms of reservoir with mercury. nhttp://www.bom.gov.au/info/aneroid/aneroid
Barograph.
Point of instruments connects with metallic aneroid. nThe recording barometer may be day and week periodical. To establish of the nperiodicals it is necessary to open the device’s case, to take down from the ndrum’s axis for the tape and on it’s nlower part to see on what period well calculated clock mechanism. 747 nMillimeter of a mercury column x 4/3 = 963 mB.This nquantity we put on the tape instead of the beginning record time.
There nis a scheme of an estimation of air behind damp: air name dry, when a water npair in this there are less than 55 %, slightly dry – at 56 up to 70 %, by nslightly wet – from 71 up to 85 %, hardly wet – have more 86 % and saturated – n100 %.
The nbusiness in that in miscellaneous terrains prevalence a direction of winds nhappens miscellaneous. What the dominating direction of winds means? This is a ndirection, which one often repeats during one year or season.
Ometeorological stations permanently registry can be defined a cosines speed of ntheir motion and directions a direction of winds on 4-8 or 16 rhombs. E – nEastern wind, that is wind, that winds from east. W- Western wind; N – Northerwind; S – Southern, NE – Northern – Eastern. At a sanitarian estimation of the projects of settlements the navailability on the schedule of a wind rose enables fast and simplly to orient and to evaluate a regularity of naccommodation miscellaneous regions, objects. For example, the regularity of nmutual accommodation of industrial firm, which one will flare air of habitatiopoint.
The nformation of gas bubbles in the organism during ascent is called decompressiosickness, known also as “the bends”.
Symptoms They noccur 5 minutes to 1 hour after the ascent, sometimes after 2-4 hours. Symptoms nrange cough, itching, reddened skin or pains in the joints to serious nrespiratory, cardiac and mental damage (such as rapid pulse and heart beat, shortness of breath, pains in the chest and stomach, nparalysis of limbs)
Treatment The nonly remedy to do away with decompression sickness is the chamber for nrecompression. The diver is exposed to the same pressure (at which he was nbefore the beginning of bubbles’ formation), necessary to dissolve the bubbles. nAfterwards, the pressure decreases on stages to avoid decompression sickness.
HOW nDOES AIR PRESSURE AFFECT THE BODY?
Air npressure is the force that is exerted on you by air molecules; the weight of ntiny air particles. Atmospheric pressure is a measure of the force exerted by nthe atmosphere, so therefore at any point on the earth’s surface, there is a nquantity of air sitting above your body. If that quantity of air is greater, nthere will be more pressure on the body; and if it is less, there will be less npressure on the body. This is traditionally measured in pounds per square inch n(PSI). 1 PSI is the force of one pound applied to an area of one square inch.
At nhigh altitudes the quantity of air is less, and the density of air is also nless. As such, there is less air pressure and as a result, less oxygen in a givevolume of air. To demonstrate this, If a person dives below the surface of nwater in scuba diving, their body has to contend with both the air exerting npressure on the surface of the water, and the water above that exerting further npressure, hence, the deeper you dive, the more pressure there is.
At nsea level, we say atmospheric pressure is 1 atmosphere (this is equal to 14.7 npsi). This arbitrary measurement provides a reference point from which we cadetermine air pressure at varying altitudes or depths.
For nevery 10 metres deep which you go in water, the pressure increases by 1 natmosphere. For example -at 10 metres it is 2 atmospheres; at 40 metres it is 5 natmospheres).
Partial nPressure Gradients
Partial npressure gradients follow Henry’s law. Henry’s law states that at a constant ntemperature, the amount of a given gas dissolved in a given type and volume of nliquid is directly proportional to the partial pressure of that gas iequilibrium with that liquid. In terms of atmospheric pressure, because a large npercentage of the body is water, as the pressure increases (i.e. as a scuba ndiver goes deeper) more gas will dissolve in the blood and body tissues. As nlong as the person remains at the same pressure, the gas will remain isolution.
The nair we breathe is a mixture of gases. Nitrogen is the most abundant gas, nand nitrogen molecules (N2) make up about 78% of our atmosphere. Oxygemolecules (O2) molecules make up about 21% of the air we breathe, water nmolecules 0.5%, and carbon dioxide 0.04%. Each of these gases contributes to nthe total pressure in the atmosphere proportional to its relative abundance.
nPartial pressure of a gas = the pressure exerted by that one gas (e.g. oxygen) nin a gas mixture (e.g. air).
The npartial pressure of oxygen is much higher in alveoli than in capillaries. That nis, there is a steep partial pressure gradient for oxygen. This partial npressure gradient causes oxygen to diffuse rapidly from alveoli to capillaries. nA similarly steep gradient affects the diffusion of oxygen from capillaries to nbody tissues. The partial pressures shown in the table below are nimportant in determining the movement of oxygen and carbon dioxide between the natmosphere and lungs, the lungs and blood, and the blood and body cells. When a nmixture of gases diffuses across a permeable membrane, each gas diffuses from nan area of greater partial pressure to an area of lower partial pressure (the ngas moves down its concentration gradient). Each gas in a mixture of gases nexerts its own pressure as if all other gases were not present.
ALTITUDES
At naltitude the air pressure decreases, so in the same volume of air, there is less molecules present (for example oxygen molecules). nPeople often say the air is “thinner” at altitude, and the result is that you nwill need to breathe faster and deeper to get the same amount of oxygen, and your nheart will pump more blood to increase the supply of oxygen to the brain and nmuscles.
Physical nperformance is affected at altitudes over 500 feet (1524 metres) the higher the naltitude, the more impaired the physical performance of the body. Physical or nwork performance is related to oxygen consumption, which decreases at high naltitudes, due to less oxygen in a given volume of air.
Endurance ncapacity is commonly measured by a reduction of 3-3.5% in maximal oxygeconsumption for every 1000 feet ascended above 5000 feet. At a height of around n25,000 feet, performance and oxygen consumption can be reduced by up to 60%.
If na person remains at high altitudes for long periods, they begin to acclimatise. nAt 9000 feet it can take 7-10 days to acclimatise. At higher altitudes it catake longer. A minority of people will never acclimatise. With acclimatisation, na person’s performance at higher altitudes will approach normal levels but nnever quite reach their norm.
Icontrast, for explosive athletic events, such as 100m sprint and long jump, nreduced atmospheric pressure results in less atmospheric resistance, so the nathlete’s performance is improved.
nEFFECTS OF CHANGES IN PRESSURE
The nskin which covers the human body will adjust to changes in pressure; however nbody cavities such as ears, sinuses & lungs, do not automatically adjust to nsuch changes.
Therefore, nthis is the reason that changes in air pressure can have the effect of causing na popping in the ears. This can occurs when flying in a plane or driving up ninto the mountains; anything where the atmospheric pressure is raised. Igeneral, the air in body cavities is normally an equal pressure to the air noutside of the body. However, if atmospheric pressure changes fast, or if there nis any blockage between the outside of the body and the internal cavities n-“equalising” of pressure might not occur properly.
A ntangible example of how you may have experienced this is when you take a drink nbottle on a flight. If you open an empty plastic bottle while you are in the nair, then tightly close it, when you land, you will find the increase in air npressure has caused the air in the bottle to compress, as if it has been sucked nout with a vacuum, and the bottle has collapsed inwards.
Whescuba diving, as the pressure increases the air spaces in a diver’s body and nequipment will compress. As the pressure decreases, the air spaces will expand. nThe amount of compression follows Boyle’s law, which describes how the volume nof gas varies, depending on the surrounding pressure.
Boyle’s nlaw is: PV = c (where P= pressure, V = volume of na gas, c = a constant)
nThis shows that when you multiply the surrounding pressure of a gas, by the nvolume of the gas, you will always have the same number. So if the amount of npressure is increased, the volume of gas must decrease, and vice versa.
The nimplications of Boyle’s law for scuba diving are that as a diver descends, the air spaces in their ears, masks and lungs are ndecreased, creating a negative pressure and a vacuum like effect. To avoid ninjury, the diver will need to equalise the pressure in the air spaces with the nsurrounding pressure (see below for more information). While they are diving, ncare must be taken to continue breathing – if a diver holds their breath and nascends to an area where less pressure is exerted, the air trapped in the lungs nwill expand and can stretch the lungs and can lead to injury. When ascending, nthe air in the diver’s ears and lungs will expand, creating a positive npressure. These air spaces can become overfull, so the diver will need to nequalise, and breath out any excess air. Failure to do nso can cause the eardrum and lungs to burst. The buoyancy compensator (BCD) nwill also expand due to decreased pressure, so the diver will need to release nair from the BCD to control their ascent. On the ascent, consideration also nneeds to be taken for the affect of Boyle’s law onitrogen gas in the diver’s body. This is explained in more depth later on ithis lesson.
How ndoes the human organism lose a heat?
Major npart of heat loses through the skin and mucous, other part goes on heating of nfood, water and breathes air. Through the skin loses main heat mass: for after none authors – 85-90%, after other – even 95%, so, only 4-6% loses on heating of nfood, breathe air and waters.
http://www.expeditionsamoyeds.org/Hypothermia.html
Because nof that interestingly will learn how the heat is lost by skin. Appear, that skin loses a heat by three ways:
•by nradiation,
•taking and
•on evaporation of nsweat moisture.
For ndata of Rubner, we can say, that man attached to nlight work in room conditions
•loses nby radiation about 40%,
•taking n- about 30% and
•by evaporation – about 20% of heat.
These nciphers are directed for orientation, and really they consider vacillate dependency on conditions.
HEAT nTRANSFER,
in physics, process by nwhich energy in the form of heat is exchanged between bodies or parts of the nsame body at different temperatures. Heat is generally transferred by nconvection, radiation, or conduction. Although these three processes can occur nsimultaneously, it is not unusual for one mechanism to overshadow the other ntwo. Heat, for example, is transferred by conduction through the brick wall of na house, the surfaces of high-speed aircraft are heated by convection, and the nearth receives heat from the sun by radiation.
Heat nTransfer Heat can be transferred by three processes: conduction, convection, nand radiation. Conduction is the transfer of heat along a solid object; it is nthis process that makes the handle of a poker hot, even if only the tip is ithe fireplace. Convection transfers heat through the exchange of hot and cold nmolecules; this is the process through which water in a kettle becomes nuniformly hot even though only the bottom of the kettle contacts the flame. nRadiation is the transfer of heat via electromagnetic (usually infrared) nradiation; this is the principal mechanism through which a fireplace warms a nroom.© Microsoft Corporation. All Rights nReserved.
CONDUCTION
This nis the only method of heat transfer in opaque solids. If the temperature at one nend of a metal rod is raised by heating, heat is conducted to the colder end, nbut the exact mechanism of heat conduction in solids is not entirely nunderstood. It is believed, however, to be partially due to the motion of free nelectrons in the solid matter, which transport energy if a temperature ndifference is applied. This theory helps to explain why good electrical nconductors also tend to be good heat conductors (see Conductor, Electrical). nAlthough the phenomenon of heat conduction had been observed for centuries, it nwas not until 1882 that the French mathematician Jean Baptiste Joseph Fourier gave nit precise mathematical expression in what is now regarded as Fourier’s law of nheat conduction. This physical law states that the rate at which heat is nconducted through a body per unit cross-sectional area is proportional to the nnegative of the temperature gradient existing in the body.
The nproportionality factor is called the thermal conductivity of the material. nMaterials such as gold, silver, and copper have high thermal conductivities and nconduct heat readily, but materials such as glass and asbestos have values of nthermal conductivity hundreds and thousands of times smaller, conduct heat npoorly, and are referred to as insulators (see Insulation). In engineering napplications it is frequently necessary to establish the rate at which heat nwill be conducted through a solid if a known temperature difference exists nacross the solid. Sophisticated mathematical techniques are required to nestablish this, especially if the process varies with time, the phenomenobeing known as transient-heat conduction. With the aid of analog and digital ncomputers, these problems are now being solved for bodies of complex geometry.
CONVECTION
Conductiooccurs not only within a body but also between two bodies if they are brought ninto contact, and if one of the substances is a liquid or a gas, then fluid nmotion will almost certainly occur. This process of conduction between a solid nsurface and a moving liquid or gas is called convection. The motion of the nfluid may be natural or forced. If a liquid or gas is heated, its mass per unit nvolume generally decreases. If the liquid or gas is in a gravitational field, nthe hotter, lighter fluid rises while the colder, heavier fluid sinks. This nkind of motion, due solely to nonuniformity of fluid ntemperature in the presence of a gravitational field, is called natural nconvection. Forced convection is achieved by subjecting the fluid to a pressure ngradient and thereby forcing motion to occur according to the law of fluid nmechanics.
If, nfor example, water in a pan is heated from below, the liquid closest to the nbottom expands and its density decreases; the hot water as a result rises to nthe top and some of the cooler fluid descends toward the bottom, thus setting nup a circulatory motion. Similarly, in a vertical gas-filled chamber, such as nthe air space between two window panes in a double-glazed, or Thermopane, window, the air near the cold outer pane will nmove down and the air near the inner, warmer pane will rise, leading to a ncirculatory motion.
The nheating of a room by a radiator depends less on radiation than oatural nconvection currents, the hot air rising upward along the wall and cooler air ncoming back to the radiator from the side of the bottom. Because of the ntendencies of hot air to rise and of cool air to sink, radiators should be nplaced near the floor and air-conditioning outlets near the ceiling for maximum nefficiency. Natural convection is also responsible for the rising of the hot nwater and steam iatural-convection boilers (see Boiler) and for the draft ia chimney. Convection also determines the movement of large air masses above nthe earth, the action of the winds, rainfall, ocean currents, and the transfer nof heat from the interior of the sun to its surface.
RADIATION
Wilhelm nWien German physicist Wilhelm Wien won the 1911 Nobel Prize in physics. His ndiscoveries in the field of radiation, including the laws that govern heat nradiation, laid the foundation for the development of the quantum theory.© The Nobel Foundation n
This process is fundamentally different from nboth conduction and convection in that the substances exchanging heat need not nbe in contact with each other. They can, in fact, be separated by a vacuum. nRadiation is a term generally applied to all kinds of electromagnetic-wave nphenomena. Some radiation phenomena can be described in terms of wave theory n(see Wave Motion), and others can be explained in terms of quantum theory. nNeither theory, however, completely explains all experimental observations. The nGerman-born American physicist Albert Einstein conclusively demonstrated (1905) nthe quantized behavior of radiant energy in his classical photoelectric nexperiments. Before Einstein’s experiments the quantized nature of radiant nenergy had been postulated, and the German physicist Max Planck used quantum ntheory and the mathematical formalism of statistical mechanics to derive (1900) na fundamental law of radiation (see Statistics). The mathematical expression of nthis law, called Planck’s distribution, relates the intensity or strength of nradiant energy emitted by a body to the temperature of the body and the nwavelength of radiation. This is the maximum amount of radiant energy that cabe emitted by a body at a particular temperature. Only an ideal body (blackbody,) nemits such radiation according to Planck’s law. Real bodies emit at a somewhat nreduced intensity. The contribution of all frequencies to the radiant energy nemitted by a body is called the emissive power of the body, the amount of nenergy emitted by a unit surface area of a body per unit of time. As can be nshown from Planck’s law, the emissive power of a surface is proportional to the nfourth power of the absolute temperature. The proportionality factor is called nthe Stefan-Boltzmann constant after two Austrian physicists, Joseph Stefan and nLudwig Boltzmann, who, in 1879 and 1884, respectively, discovered the fourth npower relationship for the emissive power. According to Planck’s law, all nsubstances emit radiant energy merely by virtue of having a positive absolute ntemperature. The higher the temperature, the greater the amount of energy nemitted. In addition to emitting, all substances are capable of absorbing nradiation. Thus, although an ice cube is continuously emitting radiant energy, nit will melt if an incandescent lamp is focused on it because it will be nabsorbing a greater amount of heat than it is emitting.
Opaque nsurfaces can absorb or reflect incident radiation. Generally, dull, rough nsurfaces absorb more heat than bright, polished surfaces, and bright surfaces nreflect more radiant energy than dull surfaces. In addition, good absorbers are nalso good emitters; good reflectors, or poor absorbers, are poor emitters. nThus, cooking utensils generally have dull bottoms for good absorption and npolished sides for minimum emission to maximize the net heat transfer into the ncontents of the pot. Some substances, such as gases and glass, are capable of ntransmitting large amounts of radiation. It is experimentally observed that the nabsorbing, reflecting, and transmitting properties of a substance depend upothe wavelength of the incident radiation. Glass, for example, transmits large namounts of short wavelength (ultraviolet) radiation, but is a poor transmitter nof long wavelength (infrared) radiation. A consequence of Planck’s distributiois that the wavelength at which the maximum amount of radiant energy is emitted nby a body decreases as the temperature increases. Wien’s displacement law, named nafter the German physicist Wilhelm Wien, is a mathematical expression of this nobservation and states that the wavelength of maximum energy, expressed imicrometers (millionths of a meter), multiplied by the Kelvin temperature of nthe body is equal to a constant, 2878. Most of the energy radiated by the sun, ntherefore, is characterized by small wavelengths. This fact, together with the ntransmitting properties of glass mentioned above, explains the greenhouse neffect. Radiant energy from the sun is transmitted through the glass and enters nthe greenhouse. The energy emitted by the contents of the greenhouse, however, nwhich emit primarily at infrared wavelengths, is not transmitted out through nthe glass. Thus, although the air temperature outside the greenhouse may be nlow, the temperature inside the greenhouse will be much higher because there is na sizable net heat transfer into it.
Iaddition to heat transfer processes that result in raising or lowering ntemperatures of the participating bodies, heat transfer can also produce phase nchanges such as the melting of ice or the boiling of water. In engineering, nheat transfer processes are usually designed to take advantage of these nphenomena. In the case of space capsules reentering the atmosphere of the earth nat very high speed, a heat shield that melts in a prescribed manner by the nprocess called ablation is provided to prevent overheating of the interior of nthe capsule. Essentially, the frictional heating produced by the atmosphere is nused to melt the heat shield and not to raise the temperature of the capsule n(see Friction).
What nis the heat losing way by radiation?
From nphysics we know, that any more heated body radiates more heat, than less nheated. So, eveot colliding with it, it gives to it its heat, while the temperatures nof both bodies will not complete with each other.
•Main room conditions is usually circled by objects with more low temperature, nthan his body, that is why takes place heat losing by radiation.
•Also nheat is lost by installation. In this case a heat is lost by two ways – conduction and convection.
•Conduction is a heat transition on the strength of ncontiguity of objects, and also air parts from more heated to less heated. Convection is a heat transmission on the strength of nmediators – air, steam, liquid, the fractions of which, heating attached to contact nwith more warm body, bear off heat and return it attached to contiguity with nmore cold objects. On the strength of temperature difference in intermediate nenvironment, for example, in air, the convectional streams are generated.
•The nthird way of heat losing is evaporatioof moisture.
A nhuman skin is always covered by sweat, water of which evaporates. For this nprocess it is necessary expenditure of warm /secretive evaporation temperature n/.
http://ppo.tamuk.edu/ehs/Heat_Stress/heatstress.htm
Microclimate –
it is meteorological nconditions in work zone, which characterized by complexes of factors that act non organism of peoples it is temperature, humidity and rate movement of air, nand also radiation temperature and warm radiation. Temperature of air is nfavorable factors which influence on heat exchange. Radioactive temperature – nit is the temperature that surround people of superficiality or intensive suor another radiation.
Microclimate nis a thermal status of the limited space. It results from combined action of nair temperature, radiation heat, air humidity and air movement velocity. nMicroclimate defines heat state of an organism. Microclimate is influenced by nlatitude, topography, human activities and vegetation as well as other factors. nSometimes they mean microclimate as variations of the climate within a givearea, usually influenced by hills, hollows, structures or proximity to bodies nof water. The warmth and humidity of the air in close proximity to a plant or nheat/moisture source may differ significantly from the general climate of the npremise.
Air ntreatment/air cooling differs from ventilation because it reduces the temperature nof the air by removing heat (and sometimes humidity) from the air. Air nconditioning is a method of air cooling, but it is expensive to install and noperate. An alternative to air conditioning is the use of chillers to circulate ncool water through heat exchangers over which air from the ventilation system nis then passed; chillers are more efficient in cooler climates or in dry nclimates where evaporative cooling can be used.
Local nair cooling can be effective in reducing air temperature in specific areas. Two nmethods have been used successfully in industrial settings. One type, cool nrooms, can be used to enclose a specific workplace or to offer a recovery area nnear hot jobs. The second type is a portable blower with built-in air chiller. nThe main advantage of a blower, aside from portability, is minimal set-up time. n
Another nway to reduce heat stress is to increase the air flow or convection using fans, netc. in the work area (as long as the air temperature is less than the worker’s nskin temperature). Changes in air speed can help workers stay cooler by nincreasing both the convective heat exchange (the exchange between the skisurface and the surrounding air) and the rate of evaporation. Because this nmethod does not actually cool the air, any increases in air speed must impact nthe worker directly to be effective.
If nthe dry bulb temperature is higher than 35°C (95°F), the hot air passing over nthe skin can actually make the worker hotter. When the temperature is more tha35°C and the air is dry, evaporative cooling may be improved by air movement, nalthough this improvement will be offset by the convective heat.
Whethe temperature exceeds 35°C and the relative humidity is 100%, air movement nwill make the worker hotter. Increases in air speed have no effect on the body ntemperature of workers wearing vapor-barrier clothing. Heat conduction methods ninclude insulating the hot surface that generates the heat and changing the nsurface itself. Simple engineering controls, such as shields, can be used to nreduce radiant heat, i.e. heat coming from hot surfaces within the worker’s nline of sight. Surfaces that exceed 35°C (95°F) are sources of infrared nradiation that can add to the worker’s heat load. Flat black surfaces absorb nheat more than smooth, polished ones.
Having cooler surfaces surrounding the worker assists in cooling nbecause the worker’s body radiates heat toward them. With some sources nof radiation, such as heating pipes, it is possible to use both insulation and nsurface modifications to achieve a substantial reduction in radiant heat.
Instead nof reducing radiation from the source, shielding can be used to interrupt the npath between the source and the worker. Polished surfaces make the best nbarriers, although special glass or metal mesh surfaces can be used if nvisibility is a problem.
Shields nshould be located so that they do not interfere with air flow, unless they are nalso being used to reduce convective heating. The reflective surface of the nshield should be kept clean to maintain its effectiveness.
HVAC n(heating-ventilation-air conditioning) system defines indoor microclimate.
A nmicroclimate maintenance system (general HVAC system) created in several rooms ngives a possibility to use an economic decision, the idea of which consists iuse of one outdoor unit and several indoor units (from two to four). It is nexplained by the fact that in adjacent room’s air-conditioners have to carry out nsimilar functions of cooling or heating.
This nmakes it possible to use one outdoor unit for work with indoor units which ncarry out cooling, for example. As a result such a system has lower operating ncosts and lower power consumption and at the same time allows you to carry out nair-conditioning in one or several rooms, where indoor units are installed.
HEAT nBALANCE
Fundamentals nof heat transfer Humans are homeothermic, which means nthey must maintain body temperature within a narrow range in varying nenvironmental conditions. The normal deep body temperature (core body ntemperature) at rest is between 36-37.5 oC, although nextremes in excess of 40 oC have been recorded iathletes and workers exposed to very severe environmental conditions. These ntemperatures are at the upper limit of human physiological tolerance, however nthey illustrate that people do get exposed to such conditions during their work npractice. The variation of resting core body temperatures also demonstrates the nindividual diversity that may exist in a working population. This variatiomeans that people may have different tolerances to working in the heat. Some npeople cannot tolerate mild increases in core body temperature whereas others, nas illustrated, can continue to work at much higher temperatures. The factors nthat may account for this variation among workers are still, however, poorly nunderstood.
Thermal nhomeostasis is maintained by achieving a balance between the various avenues of nheat gain and heat loss from the body. There are two recognised nsources of heat load;
a) Environmental, which may be positive or negative, that nis, there may be a heat gain or a heat loss from the body.
b) Metabolic, which is generated by muscular activity.
ENVIRONMENTAL nFACTORS AFFECTING THERMOREGULATION
The nprincipal methods of heat exchange between the body and the external
environment are: convection, conduction, radiation and nevaporation.
Convectio
The nrate of convective exchange between the skin of a person and the ambient air iclose proximity to the skin, is dictated by the ndifference in temperature between the air and the skin temperature together nwith the rate of air movement over the skin.
Whethe air temperature is greater than the skin temperature, there will be a gaiin body heat from the surrounding air, conversely when the skin is warmer thathe air temperature there will be a loss of heat from the body. Because warm nair rises (less dense than cool air) the warm air will rise from the body and ncool air will come in to take its place. This process is then repeated. The nprocess is called convection.
Radiatio
The nsurface of the human body constantly emits heat in the form of electromagnetic nwaves. Simultaneously, all other dense objects are radiating heat. The rate of nemission is determined by the absolute temperature of the radiating surface. nThus if the surface of the body is warmer than the average of the various nsurfaces in the environment, net heat is lost, the rate being directly ndependent on the temperature difference. This form of heat transfer does not nrequire molecular contact with the warmer object. The sun is a powerful nradiator, and exposure to it greatly decreases heat loss by radiation. When the ntemperature of the objects in the environment exceeds skin temperature, radiant nheat energy is absorbed from the environment. Under these conditions the only navenue for heat loss is by evaporative cooling.
Conductio
The ndifference between heat loss by conduction and radiation is that with nconduction the body must be in contact with the object. In such circumstances nthe heat moves down its thermal gradient from the warmer to the cooler object, nthe heat energy being transferred from molecule to molecule. The warmer nmolecule slows down after it has lost some of its heat and the cooler molecules nmove faster having gained heat. The temperature transfer continues until neventually the temperature of the two objects equalises. nThe rate of the heat transfer through conduction depends on the difference itemperature between the two objects and the thermal conductivity of the two nobjects.
Evaporatio
Whewater evaporates from the surface of the skin, the heat required to transform nit from a liquid to a gas is dissipated from the skin, this acts to cool the nbody. Evaporative heat loss occurs from the respiratory tract lining as well as nfrom the skin. There is a constant gradual loss of water from the skin that is nnot related to sweat glands. The skin is not fully waterproof and so some water nis lost out through pores in skin, and lost by evaporation. This loss is not nsubject to physiological control and is termed insensible perspiration. nSweating is an active process requiring energy and controlled by the nsympathetic nervous system. The rate at which this process proceeds can be ncontrolled and therefore the amount of heat loss can be controlled.
Radiatioand convection are insufficient to prevent warming up of the body during heavy nmanual work or at high surrounding temperatures. Under these circumstances heat nloss is aided by evaporation of water. At environmental temperatures above nabout 36 oC, heat is lost exclusively by evaporation. nAt higher temperatures heat is taken up by the body from the environment by nradiation, conduction and convection.
Sweating nthen becomes profuse in order to maintain the balance between heat uptake and nheat loss by evaporation. In order to be effective, sweat must be evaporated nfrom the skin. If sweat merely drips from the surface of the skin or is wiped naway, no heat will be lost.
Thermal nequilibrium of the body is maintained by balancing the relationship
M n± C ± K ± R – E ± S = O
Where nM = metabolic heat (always positive).
C = convective heat exchange.
K = conductance heat exchange through surfaces nin direct contact with
the skin.
R = radiative heat nexchange between skin or clothing surroundings.
E = evaporation of water from the skin surface nand respiratory tract .
S = heat storage (heat balance exists when S nis zero).
METABOLIC nFACTORS AFFECTING THERMOREGULATION
Iaddition to heat exchange between the body and the environment, internal heat nis produced by metabolic processes. Although digestion and other body processes ncontribute slightly, by far the greatest influence is the heat generated during nexternal work. Body heat is gained directly from the reactions of energy nmetabolism. When muscles become active, their heat contribution can be ntremendous. For example, at rest, the rate of body heat production is nrelatively low; the resting oxygen consumption is approximately 250 mL/micorresponding to a rate of heat production of 70W. During work, the rate of noxygen consumption can increase eightfold, and the rate of heat production is ncorrespondingly increased. There are four work components which can affect nmetabolic heat load: work rate, work nature, work pattern and posture.
Work nrate
Muscular nwork is mechanically a very inefficient process. The major muscles such as the nupper or lower limb muscles can only achieve 20-25% mechanical work efficiency. nA substantial proportion of the rest of the energy is generated as heat. There nis therefore a direct relationship between work rate and metabolic heat nproduction.
Work nnature
Much nof work is a mixture of dynamic and static components. As the proportion of nstatic work (meaning no movement) increases, the muscles become even less nefficient with the result that more energy is produced as heat. The nature of nthe work can therefore influence the metabolic heat load.
Work npattern
The role that scheduling plays in modern work can also influence nthe heat load. Set timing of breaks at work may mean that the worker ncannot stop and cool down. This may effect thermoregulatory efficiency and ntherefore work tolerance. On the other hand, self paced nwork may allow the worker to operate more safely in conditions of thermal nstress.
Posture n
The neffect of poor posture when working may place an additional burden or loading non muscles. This will result in additional heat generation by the muscles as a nconsequence of mechanical disadvantage.
THE nINFLUENCE OF CLOTHING ON THERMAL LOAD
Heat nexchange is relatively easy to analyse in the basic model, that is the exchange between human skin and the micro-climate ncreated by a layer of ambient air.
However, nwhen layers or even a layer of clothing is used heat exchange becomes far more ncomplex. The space between the skin and the outermost garment becomes a very ncomplicated micro-climate consisting of air and fabric layers changing depth nwith each body movement. The insulative ncharacteristics of this environment are given by the behaviour nof the air trapped between the skin and clothing. This means that any factor nthat alters the thickness of the air layers and so the insulative nproperties will lead to a decrease or increase in heat loss from the body. The ndifficulty of understanding the effect of heat balance is enhanced when the behaviour of the air and air exchange between the clothing nlayers and the environment is considered. The size, shape, and number of pores nin the garment influence air exchange and movement and therefore the insulative properties of the clothing. These factors iturn influence the ability of the person wearing the clothing to lose heat ngenerated by muscular activity. A change of clothing insulation is the easiest nand the quickest method of thermal adaptation, although there are practical or ncultural limits to this form of physical thermoregulation. There are cases, nhowever, where humans may adjust their metabolism rather than clothing ninsulation, as has been shown by in a North American elderly population. If the nheat generated by these factors is not lost, then a rise in core body ntemperature and heat illness will result.
The nsubject of thermal comfort is complex and beyond the confines of this work, nhowever, it is relevant to persons working in hot environments. The importance nof protecting the skin from harmful ultra-violet radiation and against non thermal hazards in the workplace is becoming nincreasingly important. Because workers should wear clothing to protect nthemselves from these hazards, the thermal properties required of clothing to maximise cooling is an important consideration. There have nbeen a number of reviews on this subject.
HUMAN nTHERMOREGULATION
It nwas previously stated that as ambient temperature increases, the effectiveness nof heat loss by radiation, conduction and convection decreases. When ambient ntemperature exceeds body temperature, heat is actually gained by these nmechanisms of thermal transfer. In such environments, or when conduction, nconvection and radiation are inadequate to dissipate substantial metabolic heat nloads, the only means for heat dissipation is by sweat evaporation. The rate of nsweating increases directly with the ambient temperature.
The ntotal amount of sweat evaporated from the skin depends on three factors:
1) nThe surface exposed to the environment.
2) nThe temperature and humidity of the ambient air.
3) nThe convective air currents around the body.
Relative nhumidity is by far the most important factor determining the effectiveness of nevaporative heat loss. When humidity is high the ambient vapour npressure approaches that of moist skin and evaporation is greatly reduced. Thus nthis avenue for heat loss is essentially closed, even though large quantities nof sweat are produced.
This nform of sweating represents a useless water loss that can lead to dehydratioand overheating. As long as the humidity is low, relatively high environmental ntemperatures can be tolerated. For this reason, hot, dry desert climates are more ncomfortable than cooler but more humid tropical climates.
Most nstudies on human thermoregulation have been performed in climate chambers as nopposed to the outdoor natural environment where most physical activity takes nplace.
The nthermal environment under outdoor conditions may include significant radiant nheat gain, especially on sunny days. For humans, the colour nof skin and clothing is of importance for the reflection and absorption of nsolar radiation, with darker colours having greater nabsorptive heat gain. It has also been reported by that the radiant heat gaifrom sun, direct and indirect, is between 160-230W per hour. It has also being nshown that the heat load gained from direct sunshine is significant, for this nreason predictions of heart rate and sweating rate based on climate chamber nexperiments will 6give too low values for outdoor exercise in the sun. Although nsolar radiation is only moderate in heat balance, the addition of this extra nheat stress, even in temperate climates, may be critical for near maximal nexercise performance, or for unacclimatised, nphysically untrained workers where thermoregulation and cardiovascular nstability become important for physical performance and endurance.
Sunstroke nis more accurately called heatstroke since it is not necessary to be exposed to nthe sun for this condition to develop. It is a less common but far more serious ncondition than heat exhaustion since it carries a 20-percent mortality rate. nThe most important feature of heatstroke is the extremely high body temperature n(105°F [41°C] or higher) that accompanies it. In heatstroke, the victim has a nbreakdown of his sweating mechanism and is unable to eliminate excessive body nheat. When the body temperature rises too high, the nbrain, kidneys, and liver may be permanently damaged. Sometimes the victim may nhave preliminary symptoms, such as headache, nausea, dizziness, or weakness. nBreathing is deep and rapid at first; later, it is shallow and almost absent. nUsually the victim is flushed, very dry, and very hot. His pupils are nconstricted (pinpointed) and the pulse is fast and strong. See figure for a ncomparison of these symptoms with those of heat exhaustion.
TREATMENT. When providing first aid for heatstroke, keep imind that this is a true life and death emergency. The longer the victim nremains overheated, the more likely he is to suffer irreversible body damage or death. The main objective of first naid is to get the body temperature down as quickly as possible.
Figure nSymptoms of heatstroke and heat exhaustion.
Move nthe victim to the coolest possible place, and remove as much clothing as npossible. Body heat can be reduced quickly by immersing the victim in a ncold-water bath. When a cold-water bath is not possible, give the victim a nsponge bath by applying wet, cold towels to the whole body. Exposing the victim nto a fan or air conditioner also promotes body cooling. When cold packs are navailable, place them under his arms, around his neck at his ankles, and in his ngroin. When the victim is conscious, give him cool water to drink Do NOT give nhim hot drinks or stimulants.
Because nof the seriousness of heatstroke, it is important to get the victim to a nmedical facility as soon as possible. Cooling measures must be continued during ntransportation.
COLD nWEATHER INJURIES
Whethe body is subjected to severely cold temperatures, blood vessels constrict nand body heat is gradually lost. As the body temperature drops, tissues are neasily damaged or destroyed.
All ncold injuries are similar, varying only in degree of tissue injury. The extent nof injury depends on such factors as wind speep, ntemperature, type and duration of exposure, and humidity. Tissue freezing is naccelerated by wind, humidity, or a combination of the two. Injury caused by ncold, dry air is less than that caused by cold, moist air, or exposure to cold nair while you are wearing wet clothing. Fatigue, smoking, drugs, alcoholic nbeverages, emotional stress, dehydration, and the presence of other injuries nintensify the harmful effects of cold.
You should also nknow that in cold weather, nwounds bleed easily because the low temperatures nkeep the blood from clotting nand increased bleeding, of course, nincreases the likelihood of shock. nAlso, wounds that are open nto the cold nweather freeze quickly. The body nloses heat in the areas naround the injury, as blood nsoaks the skin around the nwound, and clothing is usually ntorn. Therefore, early first-aid treatment becomes even more important nduring periods of low temperatures.
GENERAL COOLING (HYPOTHERMIA)
General ncooling of the entire body is caused by continued exposure to low or rapidly ndropping temperatures, cold moisture, snow, or ice. Those persons exposed to nlow temperatures for extended periods may suffer ill effects, even if they are nwell protected by clothing, because cold affects the body system slowly, almost nwithout notice. As the body temperature drops, there are several stages of nprogressive discomfort and disability. The first symptom is shivering, which is nan attempt by the body to generate heat. This is followed by a feeling of nlistlessness, drowsiness, and confusion. Unconsciousness may follow quickly. nYou will have already noted signs of shock. As the temperature drops evelower, the extremities (arms and legs) freeze. Finally, death nresults.
TREATMENT.
Hypothermia nis a MEDICAL EMERGENCY. THE VICTIM NEEDS HEAT. Rewarm the victim as soon as npossible. It may be necessary, however, to treat other injuries before the nvictim can be moved to a warmer place. Severe bleeding must be controlled and nfractures splinted over clothing before the victim is moved.
Whethe victim is inside a warm place and is conscious, the most effective method nof warming him is immersion in a tub of warm water (100°F to 105°F [38°C to n41°C]) or warm to the elbow-never hot). When a tub is not available, apply nexternal heat to both sides of the victim, using covered hot-water bottles or, nif necessary, any sort of improvised heating pads. Do not place artificial heat nnext to bare skin. When immersion is used, only the body, not the limbs, should nbe immersed. Immersion of the arms and legs causes cold blood to flow from them nto the body core, causing further detrimental cooling of the core. Dry the nvictim thoroughly when water is used to rewarm him. The most frequently nrecommended field treatment is “buddy warming.” Since the victim is nunable to generate body heat, merely placing him under a blanket or in a nsleeping bag is not sufficient. For best results, the nude victim should be nplaced in a sleeping bag with two volunteers stripped to their shorts to nprovide body-to-body heat transfer. This technique can be used by untrained npersonnel in a tent in the field and WILL SAVE LIVES!!!
Whethe victim is conscious, give him warm liquids to drink, Hot ntea with lots of sugar is particularly good. No alcoholic beverages, please.
As soon as npossible, transfer the victim to na medical facility, keeping him warm nin route. Be alert for nsigns of respiratory failure and cardiac arrest nduring transfer
Heat-Related nIllnesses – Symptoms: You will experience cramps, ndizziness, weakness, nausea, pale skin, you will be flushed, your nskill will be moist and cool, or ashen. You will also experience a rapid but nweak pulse. Possible Condition: If the victim is nexperiencing cramps get them to a cool area, give them cool water to drink; and nmassage and stretch affected muscles. If the victim is experiencing heat nexhaustion then move them to a cool place as well; make sure to loosen the nclothing so its not touching ntheir skin. Then apply wet towels directly to the skin, fan victims body; give ncool water to drink. For heat stroke, follow the same steps for heat nexhaustion. Make sure to make them rest on their side; absolutely do not let nthe victim to continue their normal activities for rest of the day and thehave them re-evaluate them the next day before allowing to return to any nphysical activities.
Hypothermia n- Symptoms: The victim will have a glassy stare, they will shiver, and experience numbness. They also nmay become unconscious. Possible Condition: The victims entire body’s temperature will loss heat and drop nbelow safe temp levels. Course of Action: First and nforemost remove any wet clothing from the victims nbody and get them dry ASAP. You will want to gradually warm the victim by nadding layers gradually. Once they have reached a safe temp put them in warm, ndry clothing and have them move to a warm, dry place. Once you have moved them nto a warm environment give them warm liquids but make sure they do not contaiany alcohol or caffeine. Usually most people think of tea but make sure its a nocaffeinated tea. The reason i keep saying gradually is cause you do not want to warm the victim to quickly or nsubmerse them in a warm bath because it could cause heart problems.
Frostbite n- Symptoms: The part of the body that is frostbittewill have a loss of sensation. The skin will appear waxy. It will also be cold nand white, yellow, blue or flushed. Possible Condition: Parts nof your body have been exposed to extremely low temperatures for an extended nperiod of time. Course of Action: Remove any naccessories from the area that has been exposed and is frostbitten. Immediately nsoak the affected area in a warm bath (make sure the water is no more then 105 degrees F) until color nand warmth returns. Dress frostbitten area with sterile dressings and bandages. nIf your hands and feet are frostbitten place the gauze between the toes and nfingers. A tip to help warm up the hands is to place them under your armpits; nand if possible place your frostbitten feet on another persons stomach. It is very important to remember nabsolutely DO NOT RUB FROSTBITTEN SKIN.
REFERENCES:
Principal:
1. nHygiene nand human ecology. Manual for the students of higher medical institutions/ Under the general editorship of V.G. Bardov. n– K., 2009. – PP. 14-34, n71-106.
2. nDatsenko I.I., Gabovich R.D n.Preventive medicine. – K.: Health, 2004, pp. 14-74.
3. nLecture non hygiene.
additional:
1. nKozak D.V., Sopel O.N., Lototska O.V. General Hygiene and Ecology. – Ternopil: TSMU, 2008. – 248 p.
2. nDacenko I.I., Denisuk O.B., Doloshickiy S.L. General hygiene: Manual for practical studies. –Lviv: nSvit, 2001. – P. 6-23.
3. nA nhand book of Preventive and Social Medicine. – Yash nPal Bedi / Sixteenth Edition, 2003 – p. n26-36, 92-97.
