314 VENTILATION 



Several years ago, Massachusetts enacted a law requiring 

 that all schoolrooms should be ventilated on practically this 

 basis. It was soon discovered, however, that such a require- 

 ment meant that practically every schoolhouse in the state 

 would have to be rebuilt or remodeled. A compromise was 

 therefore effected by which all schoolrooms were to be 

 supplied with 1800 cu. ft. of fresh air per person each hour. 

 Several other states have followed the example of Massa- 

 chusetts. It is now common practice to provide 1800 cu. ft. 

 of fresh air per person each hour in modern buildings. This 

 means that, if a schoolroom contains 30 pupils and has a fresh 

 air inlet of 4 square feet that the air must enter at the rate of 

 3.75 ft. per second. This is about the same rate of motion as 

 that of wind blowing 2J^ miles per hour, a very light breeze. 

 (Prove the correctness of this calculation.) 



344. Fallacy of This Theory of Ventilation. Students of 

 sanitation are now generally agreed that this theory of 

 ventilation, namely, that air is necessarily so vitiated as to be 

 unwholesome if it contains more than 0.06 per cent, of carbon 

 dioxide, i.e., 0.03 per cent, as in pure country air plus 0.03 per 

 cent, from breathing, is not scientifically well founded. They 

 are raising the question whether the system of ventilation 

 in common use is, after all, the best. Some are inclined to 

 question the necessity of providing so much fresh air as 1800 

 cu. ft. per person each hour. Nearly all are convinced that we 

 should give much more attention to temperature, to keeping 

 the air in the room in motion, and to the proportion of water 

 vapor in the air than we are now giving, and that possibly these 

 conditions are of even greater importance than the proportion 

 of carbon dioxide. 



In order to understand the reason for this growing belief 

 we must consider the total lung capacity of a person and the 

 volume of air he ordinarily inhales and exhales at a breath. 

 The following diagram from Colton's Physiology will aid us in 

 our study. 



