410 FOODS CIRCULATED AND USED IN THE BODY 



Need of ventilation. We have all experienced a certain dis- 

 comfort in a crowded auditorium or schoolroom after a short time. 

 Some people think that this discomfort is caused by lack of oxygen 

 in the air or by the presence of too much carbon dioxide. But 

 experiments conducted by the New York State Ventilation Com- 

 mission and in many laboratories have shown that this discomfort 

 comes largely from two sources, the rise in temperature and the 

 increase in humidity in the air. The source of this heat and 

 moisture is largely the bodies of the people who are in the room. 



In order to get rid of excess moisture, reduce the heat, and 

 remove the other products of respiration from the air, ventilation 

 is necessary. Ventilation is defined as adequate replacement of 

 used air with fresh air. In addition, air in buildings contains dust, 

 with its load of bacteria, odors of various kinds, and sometimes 

 poisonous gases. 



Methods of ventilation. Since 1800 to 3000 cubic feet of air 

 are needed by the average person each hour, various devices 

 for changing the air in rooms are used. In schools, fresh air 

 is often drawn in by fans, washed to remove dust and bacteria, 

 and then forced through ducts into the rooms, the used air in the 

 room passing out through other ducts. But recent studies in- 

 dicate that much of the expensive equipment of school buildings 

 might be discarded in favor of window ventilation top and bottom 

 with boards placed so as to prevent drafts. 



Practical Exercise 7. Make a survey of the temperature conditions in your 

 own school. Take hourly temperature records in several different rooms. 

 Make the report cover at least one week. 



A temperature of not more than 68° F. is most favorable for 

 mental work. It is found that during the winter, when artificial 

 heat is used, the air becomes too dry. Various devices are used 

 to evaporate moisture in a room and raise the humidity content 

 of the air somewhat, but no effective device is in general use for 

 keeping the humidity equal to that of the outside air. Conse- 

 quently, when we go from a warm, dry room into the cool, out- 

 of-door air, the skin becomes chilled and we may take cold. One 

 of the best ways we can keep the air in our rooms moist is to place 

 pans of water on registers or radiators. 



