CHAPTER VII. 

 VENTILATION AND HEATING DUST AND BACTERIA. 



Need of Proper Ventilation. When one is actively 

 exercising his muscles he may keep warm outdoors through 

 our winter days. For the heat of the body depends on its 

 internal fires, the oxidation of its tissues. But if we are 

 inactive, these fires burn feebly, and we need outside heat. 

 While air is free, it really costs a good deal of money to 

 have it properly warmed. 



A Lack of Effective Systems of Ventilation. Lung 

 diseases are rare in the regions where the windows and 

 doors may be kept open most of the days of the year. It 

 is from shutting ourselves in so closely that we suffer. 

 This is especially true where many people are housed in a 

 comparatively small space, as in many public buildings. 

 But in our private dwellings, even when the owners are 

 amply able to secure the most sanatory appliances, defec- 

 tive apparatus is often put in. Any system that does not 

 provide for a constant renewal of the air is defective. 



Grates as Heaters and Ventilators. Grates will aid 

 largely in renewing the air. Although in themselves they 

 merely have provision for sending radiant heat out into the 

 room and much air up the chimney, yet, without any 

 special provision for inlet of air to the room, they draw air 

 in through every crack and crevice. It would probably be 

 very much better to have special ducts for the admission 



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