Masch 31, 1911] 



SCIENCE 



487 



rangement for closing the damper of the ad- 

 mission flue every time a window was opened. 



The science of heating and ventilation may 

 be divided into two branches: (1) hygiene, (2) 

 engineering. The first includes the knowledge 

 of the effect upon health and physical and 

 mental vigor of the condition of the air in 

 buildings as regards temperature, relative 

 humidity, content of CO, and other noxious 

 gases, etc. The second includes the knowledge 

 of how to design, install and ojaerate appa- 

 ratus which will maintain the conditions that 

 are desired. The engineering branch of the 

 science is in fairly good shape. If the tem- 

 perature, humidity and CO, desired in a given 

 school room are specified, the engineers can 

 furnish apparatus which will meet the specifi- 

 cations, and whether or not the specifications 

 are fulfilled can be tested by means of ther- 

 mometers, hygrometers and analyses of the 

 air in the rooms. The hygienic branch, how- 

 ever, is in a very poor shape. It is for the doc- 

 tors to settle, and not for the engineers. 



In Dr. Gulick's address he threw doubts 

 " upon the very foundations upon which the 

 science of heating and ventilation is built," 

 that is, the hygienic foundations. He doubts, 

 I understand, if it is necessary to supply suffi- 

 cient air to keep the CO^ down to 8 parts in 

 10,000, the recognized standard. All that the 

 engineers know is that there is a tradition, 

 handed down in the text-books from time im- 

 memorial, that the CO, should not exceed this 

 limit, and on the generally accepted state- 

 ments that a man will exhale on the average 

 0.6 cubic foot of CO, per hour, and that the 

 outside air contains about 4 parts in 10,000, 

 the requirement will be met by furnishing 

 1,500 cubic feet of air per hour to each in- 

 mate. To be on the safe side, the school au- 

 thorities in Massachusetts many years ago, 

 placed in their code the speciiication that 

 1,800 cubic feet per hour should be supplied 

 for each pupil, and this requirement has been 

 placed in the statute laws of several states. 



As to the desired temperature and humidity, 

 and as to the desirability of having artificial 

 ventilation at all, the doctors disagree. Dr. 

 Gulick's letter states that Doctors Thompson 



and Brennan " think we ought to do away 

 all systems of ventilation, and use simply nat- 

 ural ventilation — open windows," while Dr. 

 Leonard Hill has found an " admirable re- 

 sult " from a plenum system, giving a moving 

 air at 57-60° F. and about 70 per cent, rela- 

 tive humidity with all windows and doors kept 

 closed. Both of these ideas are opposed to the 

 modern American system, which is a plenum 

 system maintaining a temperature of 70° F., 

 letting the humidity be what it may, with no 

 attempt to control it. A relative humidity of 

 70 per cent, at 60° F. is about equivalent in 

 actual quantity of moisture to 50 per cent, at 

 70° F., and this is probably much greater than 

 the humidity in ISTew York schools in clear 

 cold weather. 



The temperature that is desirable in school 

 rooms is probably largely a matter of habit 

 and local custom. Our people are accustomed 

 to a room temperature of 68-72°, and think 

 they like it. Englishmen in their own coun- 

 try profess to like 58-62°. Which is actually 

 the best temperature, or whether the higher 

 temperature is better here and the lower in 

 England probably no one knows. As to the 

 effect of humidity at temperatures between 

 58° and 72° F. does any one really know? We 

 do know that high humidity at 80° is much 

 more uncomfortable than low humidity at 

 90°, and we know also that regions of low 

 humidity are famous as health resorts. 



There is a vast amount of ignorance as to 

 the hygiene of ventilation. Dr. Gulick seems 

 to have an arsenal of facts ( ?) and a body of 

 " as yet undigested information " on the sub- 

 ject, and it is to be hoped that he will corre- 

 late and digest them, and present them in di- 

 gested form before some learned society and 

 have them discussed and printed for the pub- 

 lic benefit. I venture the opinion, however, 

 that all the investigations by the authorities 

 he names, after being correlated and digested, 

 are insufficient in extent and not sufficiently 

 scientific in quality to form the basis of a final 

 judgment on the disputed questions in the 

 hygiene of ventilation. 



What is needed is a new research, aided by 

 all the facilities of modern science and instru- 



