Ventilation is a process of moving foul air from any space and replacing it with fresh air. A positive displacement, however, does not take place; the incoming fresh air chiefly dilutes the foul air to a point suitable for healthful respiration.

Pure air, such as exists in the open country, contains about 4 parts of carbonic acid (C02) per 10,000 parts of air, while badly ventilated rooms often contain as. much as 80 parts of CO2 per 10,000 of air. Hygienists, after careful study, have decided that an increase of 2 parts of C02 per 10,000 of air should be accepted as the standard of respirable purity, and any excess of C02 above this may be considered as vitiation.

Production Of C02 Per Hour

Source.

Cu. Ft.

Adult man ............................................................

.6

One cubic foot of gas, burning.............................

.8

Ordinary lamp ......................................................

1.0

Candle...................................................................

.3

Taking the figures above given - 4 parts of C02 per 10,000 parts of fresh air, and 6 parts (= 4 + 2) per 10,000 of vitiated air - as the standard for proper health conditions, it is found that 3,000 cu. ft. of fresh air per hour are necessary for each adult person. If a different standard than 6 is used, the number of cubic feet per person will be found by dividing 6,000 by the difference between this standard and 4.

If any lights deliver their products of combustion into the room, the amount of C02 given off by them should be converted into its equivalent in men, thus: One ordinary gas light equals in vitiating effect about 5 1/2 men, an ordinary lamp 1 2/3 men, and an ordinary candle about 1/2 man.

It is considered good practice to allow 2,000 cu. ft. of fresh air per hour for each inmate of a room or auditorium. Hospitals and such places, where the vitiation is due to exhalations from diseased or sick people, should be provided with at least twice this amount.