VENTILATION WITHOUT FANS 



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248. Ventilation without Fans. If there is no system 

 of ventilation in the house, each person owes it to himself 

 to provide fresh air for his breathing. Natural ventilation 

 depends upon the simple fact that heating air makes it 

 lighter, so that it rises, while cooling it makes it heavier, 

 so that it falls (cf. 67). We must remember also that 

 in winter the air of the house is warmer than the air out- 

 side; hence fresh air naturally enters 

 through the cracks at the bottoms of 

 doors and windows, while the warm air 

 of the house leaves at their tops. 



Bedrooms. The windows of bedrooms 

 should be left open, unless storms make 

 this actually impossible. An excellent 

 plan, in stormy weather, is to lower the 

 upper sash a few inches. The outside 

 air then enters between the sashes, 

 while the air of the room leaves at the 

 top of the window. If a board having 

 partly boxed holes (Fig. 205) is placed under the lower 

 sash, the same result is reached. 



Bedrooms should be aired thoroughly during the day. 

 The fact that a bedroom is kept cold does not mean that 

 its air is pure; cold air may be just as foul as warm air, if 

 it is not renewed often enough. 



Gas stoves or kerosene stoves not connected with a 

 chimney are dangerous in closed rooms, since they produce 

 carbon dioxide and use up oxygen (cf. 127). 



Schoolrooms. Schoolrooms that are not ventilated artificially 

 should have each of several windows open a little, rather than one open 

 wide. In this way strong air currents (" drafts") are avoided. If the 



Fig. 205. 



How to Ventilate a Bed- 

 room in Stormy 

 Weather. 



