The fire extinguisher is a handy, recognisable, reliable and widespread safety device. However, how it actually works is not well understood, and this can lead to some dangerous mistakes in its use. For example, it is normal to keep a fire extinguisher handy in the kitchen, but is that the right type of extinguisher? Some models will make a grease fire much worse.
The first device recognisable as a modern fire extinguisher was invented by a British captain, George Manby, in 1818. It was comprised of a copper cylinder using pressurised air and pearl ash, or potassium carbonate.
In the United States, there is a fire extinguisher classification system that is coded with a letter, a colour and a symbol. Full information on the code system is provided below, under the additional Resources section.
The dry chemical fire extinguisher uses a variety of chemical combinations, but it works by projecting a powder that prevents the chemistry of heat, fuel and oxygen from igniting. An example is sodium bicarbonate, which is common for a kitchen fire extinguisher.
Foam works by putting out a thick blanket that smothers the fire, cutting off the oxygen supply. It is usually only effective for basic, combustible solids fires, but the more advanced kind is useful for combustible metals.
Another common fire extinguisher uses carbon dioxide, which packs the combination of cooling the fire while replacing the oxygen supply with a non-combustible gas. Halon is a popular cousin of the carbon dioxide extinguisher.
Inspection and Maintenance
Most fire extinguishers require inspection and maintenance every year to guarantee performance. In the United States, this service, as well as extinguisher recharging, is provided for free by local fire brigades.