Ventilation and heating : principles and application a treatise / B.F. Sturtevant Co.

Date:
[1896]
Catalogue details

Licence: Public Domain Mark

Credit: Ventilation and heating : principles and application a treatise / B.F. Sturtevant Co. Source: Wellcome Collection.

    12/180 page 6
    individual, and, while not producing sudden death, nevertheless inevitably shortens life. AIR. Air being; the prime supporter of life, health, and even life itself, are dependent upon the composition of the atmosphere. Although simply a me- chanical mixture, yet certain gases of which it is composed exist in almost un- alterable proportions in the normal atmosphere. Oxygen and nitrogen, the principal constituents, are present in very nearly the proportion of one part of oxygen to four parts of nitrogen. Carbonic acid gas, the result of all combustion, either slow or rapid, exists in the very small proportion of three to four parts in ten thousand of air, while the aqueous vapor varies greatly with the temperature and exposure to water. In addition there is generally present in air in variable but exceedingly small quantities, ammonia, sulphureted hydrogen, sulphurous acid gas, floating organic and inorganic matter and local impurities. GRAINS OF MOISTURE PER CUBIC FOOT OF AIR. Fig. l. Hygrometric Chart. HUMIDITY. The condition of the atmosphere with relation to the amount of vapor or water which it holds in suspension is expressed by the term humidity. Actual Humidity relates to the actual weight of water vapor present in a given unit volume of air, while the term Relative Humidity expresses the relation be- tween the vapor actually present in the air and that which it would contain if saturated. Obviously the air is saturated with moisture when it will hold no more. The actual humidity varies excessively with the temperature; it is, there- fore, evident that a statement of the relative humidity gives no indication of the
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