INSIDE FIRE EXTINGUSHERS
Job Specific Topics:
We talk about fire extinguishers all the time and that we need to use the correct fire extinguishers for the correct class of fire. There are many types of extinguishers on the market today, and for the most part you cannot just look at a fire extinguisher and say it is good for this class of fire, you must read the label to determine if it will put out your fire, do nothing at all to the fire or even make it worse. In this toolbox topic let’s dive into what’s inside your fire extinguisher.
Dry Chemical - This agent is made up of very small particles of sodium bicarbonate (baking soda), potassium bicarbonate, or ammonium phosphate, with additives to help enhance the flow and prevent packing and caking. Extinguishers with sodium bicarbonate and potassium bicarbonate are rated for Class B and Class C fires, while extinguishers with ammonium phosphate are rated for Class A, B, and C fires.
Wet Chemical - This agent is a water solution with additives that chemically react with fats in a cooking-oil fire, creating a thick foam blanket that will float on the surface of the oil. These extinguishers are intended for a Class K fire.
Clean Agent - This electrically nonconductive extinguishing agent, evaporates and leaves no residue behind. Currently acceptable clean agents used in extinguishers include halocarbons, such as Halotron 1 and FE36, Halon 1211, and carbon dioxide. Carbon Dioxide extinguishers are rated for Class B and C fires. Extinguishers containing halocarbons and Halon 1211 are rated for Class B and C fires, while larger units are rated for Class A fires.
Water Stream (extinguishers) - This extinguisher contains tap water or a loaded stream charge that is discharged through a hose as a solid stream. This type of extinguisher is rated for Class A fires only.
Water Mist (extinguishers) - This type of extinguisher has a special nozzle for discharging de-ionized water as a fine mist. This type of extinguisher is rated for Class A and C fires.
Foam - This extinguisher agent is either aqueous film-forming foam (AFFF) or film-forming fluoroprotein foam (FFFP). Extinguishers containing foam solution have a hose with a special nozzle that introduces air to the solution, which creates foam as it leaves the extinguisher. These extinguishers are intended for Class B fires.
Dry Powder - This agent is made up of powder or granular particles that are intended for extinguishing Class D fires. Typical dry powder agents include sodium chloride, graphite, and copper. Extinguishers containing dry powder are listed for the extinguishment of specific combustible metals.
While there are many different agents used to fight fire, as you can tell from the list above there is no single agent that is effective for all classes of fire. Although there are subtle differences in hoses and nozzles on fire extinguishers and there are various colors of fire extinguishers, they are not color coded, you must still read the label to know what class the fire extinguishers were designed to fight.
(Thanks to Lyle Cooper for this contribution)