140 



RELATION OF HEAT TO COMFORT 



It will not burn, it has greater cooling power than 

 other substances, it changes to steam and absorbs 

 large quantities of heat, and being a liquid it can be 

 thrown long distances in steady streams upon a fire. 



How is a fire extinguisher constructed and op- 

 erated? Several types of commercial fire extinguishers 

 are in general use. Figure 222 shows a carbon dioxide 

 type. Notice the small bottle at the top. It contains 

 an acid solution. In use this extinguisher is grasped 

 by the handle and turned upside down. The acid flows 

 out of the bottle and combines with the soda solution. 

 Large quantities of carbon dioxide are generated, 

 creating a pressure inside the can that forces carbon 

 dioxide and water out of the hose. The fire is ex- 

 tinguished by the cooling effect of the water and by 

 the water vapor and carbon dioxide cutting off the 

 oxygen supply. 



Another form of fire extinguisher contains the 

 chemical, carbon tetrachloride. Carbon tetrachloride 

 is a non-combustible substance that vaporizes at a low 

 temperature The vapor is about five times heavier 

 than air. When thrown on a fire the vapor forms 

 quickly and settles over it, cutting off the oxygen 

 supply. This type of extinguisher is coming into 

 greater use where a small extinguisher is practicable 

 as in automobiles and houses. It is especially useful 

 around electrical equipment because the vapor is not a 

 conductor of electricity. It is also particularly valu- 

 able for extinguishing small oil and gasoline fires 

 where water would spread the fire. 



Homes and schools should be provided with small 

 fire extinguishers and every person should be taught 

 how to use them. If a fire breaks out in your home and 

 a fire extinguisher is not available, throw water, sand, 

 or dirt on the flames to cut off the oxygen supply. If 

 some person's clothing catches on fire wrap a blanket 

 or a rug around him. Why? Instruct him not to run 

 as running makes the fire burn better. 



REFERENCES FOR FURTHER STUDY 



Texts 



Caldwell and Curtis, Science for Today, Chap. 11 



Clement, Collister, and Thurston, Our Surroundings, Chaps. 



7,8 

 Hunter and Whitman, My Own Science Problems, Unit 5; 



Science in Our World of Progress, Unit 13 (part) 



Lake, Harley, and Welton, Exploring the World of Science, 



Chap. 4 (part) 

 Pieper and Beauchamp, Everyday Problems in Science, Unit 



9 



Skilling, Tours through the World of Science, Tour 14 

 Van Buskirk and Smith, The Science of Everyday Life, 



Chap. 2 



Walking and Bedell, General Science for Today, Chap. 19 

 Wood and Carpenter, Our Environment: Its Relation to Us, 

 Chaps. 10, 12; Our Environment: How We Use and Con- 

 trol It, Unit 2, Topic 7 



Special references 



Marshall, The Story of Human Progress 



Book of Knowledge 



Williams, How It Is Made 



Forman, Stories of Useful Inventions 



Moffett, Careers of Danger and Daring 



Jewett, Town and City 



Whitman, "Fire Hazards and Safeguards," General Science 



Quarterly, March, 1920 

 National Board of Fire Underwriters, Safeguarding the 



Home Against Fire 

 Hill, Fighting a Fire 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. What the primitive methods of making fire were. 



2. The science of the match. 



3. Skill in starting a fire without the aid of a match. 



4. Skill in extinguishing fires. 



5. What common fire hazards are. 



6. The construction and operation of a fire extinguisher. 



TEST OF MASTERY OF THE TOPIC 



In your notebook complete the statements, answer the 

 questions, and comply with the instructions. 



1. What people obtained fire by rubbing together two 

 sticks of dried wood? 



2. What people obtained fire by striking together flint 

 and steel? 



3. Write a paragraph on "The Making of a Match." 



4. List here all the fire hazards you can think of. 



5. If your clothing caught on fire, how would you ex- 

 tinguish the blaze? 



6. Two chemicals used in a fire extinguisher are 



7. Write a paragraph explaining how you would build 

 a fire in the woods. 



8. If a fire suddenly broke out in your home, what would 

 you do? 



