Humidity of air
It Is caused by the maintenance of water steams in it. As well as the temperature, humidity changes depending on a climatic zone, a season, affinity of the sea. The maintenance of water steams in air is expressed in paskaljah (Pas) or in grammes in 1 m 3 air. With increase in water steams their elasticity increases in air, and at certain temperature air becomes sated (dew-point). Excess of a limit of saturation causes exudation of moisture in the form of dew, a fog, hoarfrost etc. To each temperature of air there corresponds certain limiting degree of saturation by its water steams: the above the temperature, the is more saturation degree as warm air contains bolshee quantity of water steams.
Water steams arrive in atmosphere as a result of evaporation of water from the seas, oceans, lakes, the rivers, soil, plants. In premises an additional source of humidity is the moisture evaporating from a surface of lungs, skin of people, at food manufacturing, linen drying etc.
To the humidity characteristic apply following concepts.
Absolute humidity - elasticity (pressure) of the water steams containing in air at the moment of research. It is expressed in paskaljah (Pas) or in g/m 3 .
The Maximum humidity - elasticity (pressure) of water steams at full saturation of air by a moisture prjdannoj to temperature or quantity of water steams in the grammes, 1 m necessary for full saturation g air at the given temperature.
Relative humidity - the relation of absolute humidity to maximum, expressed in percentage.
Deficiency of saturation - a difference between the maximum and absolute humidity. Relative humidity and deficiency of saturation which give representation about degree of saturation of air water steams jj have the greatest hygienic value and allow to judge intensity and speed of evaporation and #8216; sweat from a body surface at this or that temperature. The less relative humidity, the faster in such air will occur evaporation of water and that more intensively teplootdacha by evaporation. Optimum the relative humidity equal of 30-60% is considered.
The Big humidity of air adversely operates on the person. It depends on air temperature. So, at the big humidity and low temperature of air heat return by konvektsii sharply increases, that can lead to excessive cooling of an organism. G.V.Hlopin specified, that at low temperature damp air a good conductor becomes warm and causes sensation zjabkosti. The damp skin and the humidified fabrics of clothes thus also become more teploprovodnymi therefore crude air seems to colder.
Long stay of people indoors with the raised humidity and low temperature of air (more low 10-15 В°s) has harmful influence on an organism, expressed in resistibility fall to infectious diseases, and also diseases of the top respiratory ways, joints, muscles and peripheral nerves. From clinical supervision it is known, that the crude and cold climate conducts to increase of disease by a diphtheria, a tuberculosis, a nephrite etc.
At high humidity and temperature of air the basic way of return of heat - evaporation, i.e. potootdelenie. However intensity and speed potootdelenija depend on humidity of air more. The above humidity of air, the occurs evaporation from a skin surface in this connection human body overheating is possible more difficultly. The general state of health thus worsens, working capacity goes down.
From the told follows, that air with high humidity under any, temperature conditions is harmful to an organism. Dry air is transferred easier. Adverse influence of dry air is shown only at the relative humidity equal less of 20%, and expressed by sensation of dryness of a mucous membrane of respiratory ways.
Non-uniform heating of a terrestrial surface is the reason of movement of air. Movement of air beds in a horizontal direction is called as a wind. Speed of movement of air (wind) is expressed in metres per second. Movement of air with a speed more than 1 km/s is perceived as a wind, and less 1 km/s not felt as a human body. At speed more than 5-7 km/s are shown irritating action of a wind. Influence of movement of air on a thermal exchange is expressed in increase in return of heat of an organism first of all for the account konvektsii as moving air carries from a body nagretye, adjoining sloivozduha, and on their place colder come. And such change of air at the expense of its movement during the summer period plays a positive role as warns overheating, and in the winter - negative, promotes organism overcooling. The wind is reflex strengthens also metabolism processes: Raises teploproduktsija in process of fall of temperature and increase in speed of movement of air.
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