THE AIR AND VENTILATION 23! 



SUMMARY 



1. Air is essentially oxygen diluted with four times its 



volume of nitrogen. 



2. When the amount of oxygen is diminished there is 



shortness of breath. 



3. Exhaled carbonic acid gas is not poisonous in itself, 



but if present in great amounts it may keep oxygen 

 out of the lungs. 



4. Foul-smelling vapors, carbonic acid gas, moisture, and 



the contamination by fire and lights make the air of 

 crowded rooms oppressive. 



5. Coal gas inhaled may unite with the hemoglobin in the 



red blood cells so that they will not carry oxygen. 



6. The main thing to be feared in close air of crowded 



rooms is the disease germs which may be breathed 

 into it. 



7. The air of a room should be changed often enough to 



allow 4000 cubic feet of fresh air to each person 

 each hour. 



8. Breathed air is warm, and tends to rise and pass out of 



cracks and openings in the upper part of the rooms, 

 while cold, fresh air enters by lower openings. 



9. In large buildings the foul air is either forced or 



drawn out by rotary fans, and fresh warmed air 

 enters to take its place. 



IO. The atmosphere is purified by winds, rain, sunlight, 

 and plants. 



DEMONSTRATIONS 



93. The harmlessness of carbonic acid gas can be illustrated by 

 soda water, which is water in which a large amount of the gas is held 

 under pressure. Open a bottle and inhale the liberated gas. Notice 

 its pungent odor and taste. 



