THE CONTROL OF HEALTH 387 



raised to such a degree that the radiators can be made very 

 hot in severe weather and every room thoroughly warmed. 

 The objections to steam heat are: The air of a room is heated 

 over and over with no ventilation unless such is specially 

 provided; the radiators may become over-hot and "burn up" 

 the air; and no heat is obtained from the fire till the water is 

 near the boiling point. 



Hot Water System: This has the advantage of delivering 

 some heat to the radiators as soon as the water is slightly 

 warm. The heat is steady, and the radiators remain warm a 

 long time after the fire is low. The disadvantages of this 

 heating plan are that the radiators never get so warm as with 

 steam, and must therefore be much larger for the same service; 

 furthermore, ventilation must be secured in ways not related 

 to the heating system. 



Ventilation. Ventilation is necessary for several reasons : 

 breathed air contains too little oxygen, too much CO 2 , too 

 much moisture and too many organic compounds in small 

 amounts. Each person vitiates about 1,800 cubic feet of 

 air per hour, and provision must be made for its renewal or the 

 individual becomes inefficient in working power and in resis- 

 tance to disease, and is reduced to poor health generally. 



Of all the many ways of letting fresh air into rooms, the 

 old-time method by way of windows and doors is one of 'the 

 best; forced ventilation with flues and fans is seldom entirely 

 satisfactory and is very expensive. A good way to ventilate 

 a room is to let fresh air enter near the top of the room, and to 

 let the stale air escape at the bottom as through a fireplace or 

 some similar exit. Fresh air is bound to enter around loose 

 windows and doors. 



Especial provision must be made for all buildings where 

 many people congregate as in schools, churches, and theatres. 

 Sufficient air space cannot be secured for such rooms unless 

 they are made very large, or with high ceilings. No drafts, 

 either warm or cold, should be allowed during cold weather; 



