342 VENTILATION 



the atmospheric pressure forces the soda water. When we 

 clean a carpet by means of a vacuum cleaner, the tool fits 

 tightly against the top surface of the carpet. In entering the 

 tool the air must come up through the carpet; as it does so it 

 carries all loose dust and dirt with it. 



Exercise 75. A Study of Vacuum Cleaners 



Study several different types of home vacuum cleaners, determin- 

 ing exactly how they work. Write a description of one or more of 

 the cleaners studied. 



