248 DUDLEY — PASSENGER CAR VENTILATION. [Aprils, 



final solution, it certainly can be justly claimed that it is a marked 

 amelioriation of the conditions which have prevailed heretofore. 



Before proceeding to describe the system, it may perhaps be wise 

 to consider briefly a few preliminary questions as follows : 



First, is it possible to properly ventilate a car without having the 

 heating system a part of the ventilating system ? It will be quite 

 obvious on a moment's reflection, we think, that in the climate in 

 which we live unwarmed air, especially in view of the large amount 

 of it required, as will appear later, cannot be successfully taken 

 through so small a space as a passenger coach in sufficient quantity 

 to properly ventilate it. Little argument is needed on this point, 

 and in the system to be described the heating system has been 

 regarded as an essential feature. A few proposed systems have 

 ignored the heating system, but none of them, so far as known, can 

 be regarded as efficient in cold weather. 



A second point that deserves a moment's attention is, ''When 

 can a space be said to be well ventilated, or what is the standard 

 of good ventilation?" It is well known that three things are con- 

 tinually given ofl" from the bodies of human beings which tend to 

 make any space in which they are situated for any length of time 

 have the characteristic which is called "ill ventilated." These 

 three things are carbonic acid, water vapor, and a certain sub- 

 stance which for want of a better name is commonly called " organic 

 matter," and which is believed to be the source of the odor. Of 

 these three, carbonic acid is easily determined. Those who are 

 familiar with the studies that have been devoted to ventilation, and 

 which are described in standard works on Hygiene, are aware that 

 formerly an arbitrary amount of carbonic acid in the air was taken 

 as the measure of good ventilation. It is well known that the 

 ordinary outside air contains about four cubic feet of carbonic acid 

 in 10,000 of air, and formerly it was customary to say that if the 

 carbonic acid in any closed space occupied by human beings did 

 not exceed ten cubic feet per 10,000, the space might be regarded 

 as well ventilated. Later studies seemed to have changed this view, 

 and the test that is now given in the standard works on ventilation 

 is that a space can be said to be well ventilated when a person 

 coming into that space from the outside air does not detect any 

 of the odor which is characteristic of badly ventilated spaces. 

 Quite a large number of analyses have been made to determine how 

 much carbonic acid is characteristic of air of this kind. The best 

 and most careful studies on this subject are probably those given 



