The contents of a fire extinguisher depend on the type of extinguisher. Fire extinguishers are handheld active fire protection devices that are usually filled with a dry or wet chemical used to extinguish or control small fires. Here are some of the most common types of fire extinguishers and what they contain:
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Water-based fire extinguishers: These contain a pressurized canister of water and compressed gas, such as nitrogen, carbon dioxide, or argon. The gas fuel helps to expel the water from the extinguisher with enough force to break through the flames and cool the area around the fire. The water does not extinguish the fire; it only takes away the heat.
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Carbon dioxide fire extinguishers: These contain carbon dioxide, which is used as a fire-extinguishing agent because it suppresses the combustion reaction by displacing oxygen. Carbon dioxide is also used in mission-critical applications such as data centers, where suppression of a fire with water would damage equipment.
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Dry chemical fire extinguishers: These contain a powder-based agent that extinguishes by separating the three parts of the fire triangle. It prevents the chemical reactions involving heat, fuel, and oxygen, thus extinguishing the fire. The substances in dry chemical extinguishers can stop this process.
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Soda-acid fire extinguishers: These contain sodium carbonate and a flask of acid. If the flask is broken, a chemical reaction releases a stream of frothy water.
Fire extinguishers are generally effective only when used on small, contained fires. They are not intended for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user, or otherwise requires the equipment, personnel, resources, or expertise of a fire brigade.
