HUMIDITY AND TEMPERATURE OF AIR

Humidity

Water vapor is present at all times in the atmosphere. It is the least constant of all of the air constituents, varying greatly under different conditions. The temperature produces a greater change in the amount of aqueous vapor in the air than any other factor. There may be so much water vapor in the air that the air is spoken of as being completely saturated. This is known as absolute humidity. If there is any excess over and above this complete saturation, it is given off as dew; it is spoken of then as having reached the dew point. It must be remembered that this absolute humidity does not represent a constant amount of water vapor, for the amount of moisture necessary to produce complete saturation varies with the degree of temperature. It is erroneous to speak of the air holding water.

“As a matter of fact, the air has nothing to do with it, for it has always been clearly observed that the presence of water vapor in any given space is independent of the presence or absence of air in the same space. The amount of aqueous vapor which a space contains depends entirely upon the temperature and not upon the presence of the air.”—Rosenau in Preventive Medicine and Hygiene.

The higher the temperature the greater the amount of water vapor in one cubic foot of air at a temperature of 10° F., while at 100° F. there would be 19.1 grains at complete saturation. Since increased temperature increases the amount of aqueous vapor and this aqueous vapor in turn absorbs heat, we thus see a reciprocal action of the aqueous vapor upon the temperature.

Absolute humidity is all of the water vapor that may be contained in the air at a given temperature. Relative humidity is the difference between the amount of water vapor that must be contained in the air at a given temperature to reach absolute saturation and the amount actually contained in the air at that same temperature.

If the relative humidity of the air in a room becomes as high as 85% the moisture will begin to condense and form on the walls and objects. This makes the room damp and interferes with the ventilating and heating of the room.

There is less water vapor contained in the air at high altitudes, the air being cooler. A large amount of rainfall does not necessarily produce an increase in the relative humidity. That is to say, a country with a very high average of rainfall is not necessarily a damp country so far as the atmosphere is concerned.

Cold Dry Air

Cold dry air is exhilarating and tends to quicken metabolism in the body, while warm damp air is depressing and tends to retard metabolism.

The body possesses great possibilities of adaptation to the varying degrees of temperature and humidity through the action of Innate Intelligence. With the aid of the educated mind in bringing about adaptation in the way of clothing, for example, it is possible to increase the range of temperature and humidity to which the body may be adapted.

Due to the fact that heat is being constantly formed in the body by the different processes that are carried on within, it naturally follows that this heat must be carried out of the body or it will accumulate and result in harm to the tissues, producing what is known as heat stroke. This heat dissipation is greatly influenced by the humidity, or in other words, the amount of water vapor in the air. The temperature of the air also has some influence on heat dissipation.

Cold air is made to feel colder by an increase in the amount of moisture while warm or hot air is made hotter by increasing the moisture. The reason for this is that the moisture in the cold air favors heat conduction, hence draws the heat from the body at a more rapid rate than is normal, while the moisture in the hot air hinders evaporation.

Innate Intelligence is able, through the specially devised machinery of the body, to maintain a perfect balance between heat production and heat dissipation or heat loss. Even though the temperature of the air may rise, yet if the body is normal it will not produce an increase in the bodily temperature. Indeed, it is asserted that when the temperature of the air goes above 70° F. the bodily temperature would rise if it were not for the perspiration which Innate will produce through the sweat glands. As long as the perspiration is produced and is evaporated from the surface of the body the heat production and heat loss will be kept in perfect balance. But when something interferes with this adaptative process of Innate and the individual can not perspire, there will soon be symptoms of overheating and the temperature of the body will begin to rise.

Evaporation is decreased in an atmosphere in which the humidity is high. The reason for this is obvious; the atmosphere already filled with water vapor is slow to take up more. This is because molecules of vapor given off from the body collide with those in the air and are returned to the surface of the body as moisture. When this condition obtains there is an adaptation produced by increasing the amount of blood to the skin; this increases the temperature of the surface of the body, but allows for an increase in the heat loss by radiation, conduction and convection.

The conductivity of the atmosphere for heat is increased by an increase in the humidity; hence a cool damp air will chill the body for the reason that the conductivity is increased and bodily heat is lost more rapidly through conduction. Increased humidity interferes with the evaporation of perspiration; hence a hot, moist air is heating to the body and deprives the body of force, making the patient feel sluggish and fatigued.

There is much moisture given off from the body each day. It is estimated by Pettenkofer, Voit, Rosenau and others that the average individual under ordinary circumstances will give off through the lungs about 290 grams, and from the skin from 500 to 1800 grams daily. If this fact is kept in mind some idea of the necessity of proper ventilation will be appreciated.

Warm Moist Air

Workers fatigue much more easily when in warm moist atmosphere. Work is done much more rapidly in cool dry air and the efficiency of the worker is noticeably raised; in warm damp air the bodily temperature rises and the pulse rate increases.

Mental and physical activities are reduced in an atmosphere of high humidity and increased temperature. This is due mainly to the reluctance on the part of the individual to put forth an effort sufficient to perform any great amount of work. There is a general feeling of languor because of the enervating effect of the air.

There is no serious injury resulting from working in such an atmosphere, unless there is an increase in the bodily temperature, and then there may be serious results to the health unless relief is obtained. When the humidity has reached the point of complete saturation and the temperature is above 88° F., compensation can no longer obtain through evaporation and heat stroke may result. The most noticeable effect of warm moist air under ordinary circumstances is reluctance to put forth any mental or physical exertion, and a loss of appetite. With a temperature at 75° F. and the relative humidity 80%, an individual not accustomed to such will require complete rest.

It will be noticed that under such conditions Innate Intelligence is constantly working to bring about intellectual adaptation and that she is able to do so to a remarkable degree. The glands of the body are used to produce secretions which constantly bathe the tissues and keep them cool in the high temperatures, and at a proper degree of warmth in the low temperatures. The fact that the individual is indisposed to mental and physical activity in such an atmosphere is adaptative on the part of Innate. This inactivity is suggested by means of the languid feeling in order that the body will not be over-exercised and thus will not increase the amount of heat in the body; because under these circumstances the process of evaporation is interfered with and this is one of Innate’s principal means of regulating the temperature of the body.

Perspiration is an adaptation on the part of Innate, for in this way the surface of the body is kept moist and as this moisture evaporates the body is cooled; otherwise the temperature of the body would increase with every rise in the temperature of the atmosphere. Not only does this help to regulate the bodily temperature, but it keeps the surface tissue of the body soft. If there was no perspiration, the surface of the body would soon become dry, parched and hard. The skin would become scaly and would crack and become chafed.

Because of these adaptative processes it is possible for the body to be adjusted to great extremes in temperature. The body may become accustomed to extremely high temperatures even with high relative humidity, providing the change takes place gradually and sufficient time is allowed for the processes of adaptation to take place.

It is very important that the kidneys be able to perform their normal function in order that these processes of adaptation may take place. The kidneys are important not only because of the function which they perform in the excretion of poisons, but because of the function which they perform in relation to the serous circulation. This is important because of the secretions that are involved. This subject will be treated more fully under the subject of Water.

Cold Damp Air

The body quickly becomes chilled in a cold damp air because the increase in the water vapor increases the conductivity of the air for heat. It can thus be seen that the heat producing processes of the body must be increased in order to maintain the normal temperature of the body. As we know, all activity of the body requires an expenditure of energy, so if the body is exposed to a cold damp air for an abnormal length of time it will necessitate an increased expenditure of internal energy to meet the increased demands for heat and thus dissipate forces that should and would, under normal conditions, be utilized in the metabolism of the body. If the heat production is at a minimum in the body, which it may be, due to several factors such as old age, infancy, or dis-ease, this exposure to lowered temperature and high humidity will result in injury to the body.

An interference with the transmission of mental impulses to the kidneys resulting in a decrease in their functional activity may mean a retention of poisons in the body and produce a condition diagnosed as rheumatism, for example; or an interference with the serous circulation may result in the tissue cells being under-nourished. Both of these conditions will interfere with the processes of intellectual adaptation. Educationally, man may help in the adaptation by proper clothing and by giving attention to proper exercise.

Warm Dry Air

By far the most desirable air is the warm, relatively dry air; but as has already been noted, it is possible to have an atmosphere with a relative humidity that is too low. If the air is abnormally dry, and at the same time warm, there will be a great loss of body moisture due to the increased evaporation. When the loss of water from the body reaches 21% death ensues. In an experiment performed by Rubner and Lewaschew it was found that a man weighing about 127 pounds gave off about 54.1 grams of water in an hour in a temperature of 68° F. with a relative humidity of 82%; the same individual in a temperature of 68° F., but with a relative humidity of 82%, gave off only 15.3 grams.

Proper Temperature and Humidity

The most desirable atmospheric conditions are obtained at a temperature of 68° F. to 70° F., with the relative humidity from 40% to 60%. This is given only as a general average and will necessarily vary with many conditions, such as seasons of the year and occupation.

Moderately cool and relatively dry air increases the activities of the body, makes breathing easy and more frequent, and hence increases the circulation of the blood. Innate is thus enabled, in such an atmosphere, to bring about more perfect metabolism.

Proper temperature and humidity of the air in houses, impurities found therein, source of impurities and their effect upon health, will all be considered thoroughly under Hygienic Housing.