FRESH AIR 323 



the conclusion that "the chance of direct bacterial infection through the 

 air of drains and sewers is so slight as to be practically negligible." 

 He says: 



If one were to breathe for twenty-four hours the undiluted air of a house 

 drainage system, at any point not immediately infected by mechanical splashing, 

 it appears that less than fifty intestinal bacteria would be taken in. . . . There 

 would be less danger of contracting disease from continuously breathing the air 

 of a vent pipe, except where liquid is actually splashing, than from drinking 

 New York water. 



Workmen in sewers are notoriously strong, vigorous, healthy men, 

 with a low death rate among them. With such facts before us the 

 specter of an invisible monster entering our homes surreptitiously from 

 our plumbing pipes and sapping our lives and the lives of our children 

 must be laid aside; we need no longer leave saucers of so-called 

 " chlorides" standing about our floors to neutralize in an impossible 

 manner mysterious effluvia that do not exist; and when we return to 

 our town houses in the autumn we may enter them with no fears that 

 we are risking our lives by coming into a toxic, germ-infected, sewer- 

 gas-laden, deadly atmosphere. 



Our consideration so far of the qualities of air and their relation to 

 human beings has been mainly destructive. I have tried to make it 

 clear that we must give up some of our long-cherished notions. We 

 have seen that while air may be rendered unsuitable for respiration by 

 Tery unusual means, such as the addition of poisonous gases or excessive 

 quantities of irritating dust or bacteria, the vitiation of air by the pres- 

 ence within it of human beings is not due, except under the most rare 

 and exceptional circumstances, to chemical changes produced therein by 

 respiration, such that when the air is rebreathed it reacts harmfully 

 through the blood on the bodily tissues. The claims that are sometimes 

 made by the venders of commercial chemical air-purifiers on behalf of 

 their machines are based upon entire ignorance of the facts. 



Nevertheless, that the air of a confined, ill-ventilated room when 

 crowded with human beings soon becomes bad can admit of no ques- 

 tion, and we are forced to search further for its bad qualities. Science 

 has in recent years apparently found them in the physical, rather than 

 the chemical action of such air on the body. This conclusion has been 

 reached, not so much through inability to find the evil in other features, 

 as through the very positive results of many experiments made by 

 different investigators. 



The human body is constantly burning fuel within itself and pro- 

 ducing heat in the process. The amount of heat thus produced during 

 twenty-four hours by an average adult man, when at rest, is about 2,400 

 calories, which is equal to the heat evolved by four or five ordinary 

 Tungsten electric lamps during the same time. Such a man doing hard 



