VENTILATING THE HOME 21 



body is too cool, the arteries contract and less blood is sent 

 to the skin, and the activity of the sweat glands is lessened. 



The ill effects of lack of ventilation are due largely to 

 interference with this heat-regulating mechanism. Recent 

 experiments show that these ill effects are due chiefly to 

 four causes: (i) lack of air currents, (2) unpleasant odors, 

 (3) too high a temperature, (4) too little or too much moisture 

 in the air. 



Essentials of ventilation. A proper system of ventila- 

 tion should therefore do these things : 



1. It should furnish a gentle current of air. 



2. It should change the air so as to keep it free from dis- 

 agreeable odors. 



3. It should heat this air to the proper temperature, not 

 to exceed 70 degrees. 



4. It should add moisture to bring the air up to the proper 

 degree of humidity, from 50 to 60 per cent. 



Air currents. In order to meet the first and second con- 

 ditions, each room in the house should have two openings, 

 one by which the fresh air may enter and another by which 

 the used air may leave. The inlet for fresh air may be pro- 

 vided by means of registers connecting with pipes which 

 lead to the fresh air supply heated by the furnace. The 

 outlet for the used air may be provided by means of a fire- 

 place flue, with which each room may be connected by a 

 short pipe, or the outlet may be provided directly by the open 

 fireplace itself. A change of air may also be brought about 

 through the use of windows and doors. 



The common notion that drafts are injurious is a mistaken 

 one, as they are essential to good ventilation. You do not 

 take cold when out in the wind if you are properly clothed. 

 When sitting indoors, it is well to guard against exposing a' 

 small part of the body to a very cold, strong draft ; but 

 some motion of air is essential to our comfort and health. 

 If there is no movement of air, the layer of air next to the 



