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Dry chemical fire extinguishers are the most commonly used fire extinguishers in households.Important Insights
- Fire needs three elements to ignite: fuel, oxygen, and heat. Eliminating one of these factors will put out the fire.
- Dry chemical fire extinguishers operate by smothering the flames, effectively cutting off the oxygen supply to the fire.
- The extinguishers discharge a fine powder, such as sodium bicarbonate, potassium bicarbonate, or monoammonium phosphate, which coats the fuel and deprives it of oxygen, thereby extinguishing the fire.
Ask any firefighter what it takes to start a fire, and they'll tell you that three key elements are required:
- A fuel - You require a combustible solid, liquid, or gas of some kind.
- Oxygen to combine with the fuel.
- Heat - The fuel must be heated to a sufficient temperature to reach its flash point. For instance, the paper on your desk is surrounded by oxygen but will not ignite unless it is heated enough.
To extinguish a fire, one of the three necessary components must be removed. When firefighters are tackling a forest fire, they usually focus on removing either the fuel or the heat. They may either douse the flames with water to lower the temperature or clear areas of fuel by bulldozing strips of bare earth.
A carbon-dioxide fire extinguisher works by replacing oxygen with carbon dioxide. You could use any non-oxidizing gas (such as nitrogen) for this purpose, but carbon dioxide is affordable and simple to store.
Another method to cut off oxygen is by draping a blanket over the fire. Covering it with dirt or sand has the same effect. You might have heard that throwing baking soda or salt on a kitchen fire will extinguish it. Throwing sand would work in a similar way, but most people tend to have more salt than sand in their kitchens.
Dry chemical fire extinguishers are the most widely used fire extinguishers in homes. They can handle all three types of fires commonly found in kitchens or workshops: combustible solids like wood or paper, flammable liquids such as gasoline or grease, and electrical fires. The principle behind a dry chemical extinguisher is to cover the fuel with an inert solid (similar to dirt or sand). The extinguisher releases a fine powder made of sodium bicarbonate (NaHCO3, also known as baking soda), potassium bicarbonate (KHCO3, nearly identical to baking soda), or monoammonium phosphate ((NH4)H2PO4). These powders coat the fuel and smother the fire.
