There are different types of fire extinguishers designed for specific fire classes. Class A extinguishers use water or water with additives to fight fires fueled by ordinary combustibles like wood. Class B extinguishers contain chemicals to smother liquid fuel fires using pressurized water, foam or dry powder. Class C extinguishers are for electrical fires and use non-conductive agents like carbon dioxide or dry chemicals. Additional classes include Class D for combustible metal fires and Class K for cooking grease blazes. Each type works through mechanisms like cooling, oxygen removal or chemical suppression of the fire's chemical reaction.

1. Fire Extinguishers How they work and the different purposes

3. At the end of the 19 th century there was the invention of the Soda-Acid extinguisher. This cylinder contained 2 gallons of water that had sodium bicarbonate mixed with it. Inside the cylinder was a container that had concentrated sulphuric acid. Once the handle was pulled it would break the container causing a reaction that would make carbon dioxide that forces the water out of the cylinder under high pressure.

5. The Five Classes are A, B, C, D, and K

6. Fire extinguishers are designed specially for these different classes of fires. Often times because of chemical reactions within the fire more then one type of extinguisher is effective.

8. Class B – Used for putting out fires fueled by liquids or grease. The symbol used to identify is a square around the letter B.

9. Class C – Used for putting out electric fires, the mixture inside the cylinder is non conducting so that the user is not electrocuted.

10. Class D – Used to put out fires on flammable metals or other toxic chemicals. The symbol is a star around the letter D. These extinguishers are much more expensive then the other extinguishers and require special training to operate.

11. Class K – Used to put out kitchen fires or areas that have a high probability of a grease fire. This class has only been around since 1998 so there are fewer of them.

14. Wetting agents are also added so that the water sticks to the surface.

15. Water extinguishes fires because the water cools the fire below its ignition point, and large amounts of water can also deprive the fire of oxygen.

16. Water will not work on all types of fires, if water is sprayed onto burning liquid petroleum will just spread the flames around more. And water sprayed on an electric fire will cause the user to get shocked.

18. Common foams are meant to only work on nonpolar flammable liquids such as petrol, but break down too fast to work on polar liquids like alcohol. Polar liquids have another foam called “alcohol foam”.

20. This powder is a mixture of sodium bicarbonate and calcium carbonate made into a fine powder. It is propelled by carbon dioxide or nitrogen.

21. When this is sprayed onto a fire it interfere with the chemical process of fire. Along with some cooling and exclusion of oxygen.

22. These extinguishers are good for knocking down big class B flames but will not keep the fire suppressed.

23. Many times dry powder will be used with foam extinguishers for attacking large class B fires.

26. Commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap.

27. Once the extinguisher is sprayed it converts the burning substance to a non-combustible soap. This also has a cooling affect and suppresses the flames with the mist,

29. It is very commonly used on electrical fires because it being a gas does not leave any residue harming the equipment.