

VENTILATION. 357 



VENTILATION. 



In the open air the effects of respiration on the atmosphere can- 

 not be appreciated, but in inclosed spaces, such as houses, rooms, 

 etc., which are occupied by many persons, the air soon becomes 

 appreciably changed by their breathing. 



The most important changes are (1) removal of oxygen, (2) 

 increase in carbonic acid, and (3) the appearance of some poison- 

 ous materials which, though highly injurious, cannot be deter- 

 mined. The deficiency in oxygen never causes any inconvenience, 

 as it is never reduced below what is sufficient for the saturation 

 of the haemoglobin. The excess of CO 2 seldom gives any in- 

 convenience, since the air becomes disagreeably fusty or stuffy 

 from breathing long before the amount of CO 2 has reached 0.1 

 per cent., which amount of pure CO 2 can be inspired without 

 any unpleasantness. It is, then, the exhalations coming from 

 the lungs, and probably skin, some of which must have a poison- 

 ous character, that render the proper supply of fresh air impera- 

 tive. 



The difficulty of determining the presence of the poisonous 

 organic materials, makes it convenient to use the amount of CO 2 

 present in the air as the means of measuring its general purity. 

 We suppose, then, that the relation between the poisonous organic 

 ingredients and the CO 2 is constant. 



Air, which is rendered impure by breathing, becomes disagree- 

 able to the sense of smell when the CO 2 has reached the low stand- 

 ard of .06 or .08 per cent. ; that is to say, scarcely twice as much 

 CO 2 as is contained in the pure atmosphere. Supposing that air 

 is unwholesome when its impurities are appreciable by the senses, 

 then, if the animal body be the source of the CO 2 , .06 per cent, of 

 this gas makes the air unfit for use. 



An adult man disengages more than half a cubic foot of CO 2 

 in one hour (.6 Parkes), and consequently in that time he renders 

 quite unfit for use more than 1000 cubic feet of air, by raising 

 the percentage of CO 2 to .1 (.04 being initial, and .06 respiratory). 



It is obvious that the smaller the space and the more confined, 

 the more rapidly will the air become vitiated by respiration. It 

 becomes necessary for health, therefore, to have not only a certain 



