Water Fire Extinguishers
Water fire extinguishers are used on Class A fires, which usually involve freely burning solid materials such as paper, wood, straw, fabrics and coal. The extinguisher works by spraying a jet of water onto the fire, which penetrates the fire and extinguishes the flames by cooling the burning materials and preventing them re-igniting. Ordinary water fire extinguishers should not be used on fires with electrical equipment because water is conductive so could lead to an electric shock if used on anything electrical. There are several main types of water fire extinguishers, which are the standard ones, spray mist extinguishers and water additive extinguishers. Standard models use ordinary tap water which is sprayed out in a jet under pressure from compressed air. The spray mist type extinguisher produces a fine mist of de-ionised water, which prevents conduction of electricity and risk of electrocution if it is accidentally sprayed on electrical equipment. It should not be used as a solution for dealing with electrical fires, but it does mean it is more versatile and is definitely safer than a standard water appliance if electrical equipment is encountered near the fire. The fine spray also improves the soaking and cooling ability of the extinguisher, though you need to fight the fire from a closer range than with the standard water fire extinguisher. The water additive type has an environmentally friendly additive in the water which significantly increases the effectiveness of the extinguisher by reducing the surface tension of the water. It means that, compared to a standard water fire extinguisher, a water additive appliance can be smaller and lighter, and still be more effective than the ordinary extinguisher. It often also comes with a spray type nozzle. Their suitability for use on most common materials makes water fire extinguishers the basic fire fighting tool of choice, particularly in offices, warehouses, schools, and many other workplaces.