358 APPLIED SCIENCE 



victim of the disease long before it is known. Sputum cast 

 about upon the floor and elsewhere becomes dried on ex- 

 posure to the air and then ground to powder, the bacilli 

 spreading in all directions. 



Enough has been said to show the need of a systematic 

 method of removing the waste gases, dust, etc., from rooms 

 and buildings. Natural agencies, like the air, that pass 

 through the cracks of floors, doors, and windows may be 

 sufficient to remove some of the carbon dioxide of a dwelling 

 house by replacing it with new air, but in a factory where 

 hundreds of people are employed in the same rooms this 

 method is ineffective. 



Questions 



1. What is ventilation? 



2. Why is ventilation necessary? 



3. What are the different methods of ventilation? 



4. Describe each method of ventilation. 



5. What are the waste products of industrial processes? 



6. Describe the changes that take place in the human body and 

 some of the waste products. 



7. Name some noxious gases and the evil effects produced by 

 them. 



8. Name some of the forms of dust found in industries. 



9. What are some of the causes of tuberculosis? 



