Water fire extinguishers work primarily by cooling the burning material below its ignition temperature, thus removing the heat element essential for the fire to continue burning. They discharge a stream or spray of water at high pressure onto the fire, cooling the flames and the burning surface to stop combustion. Water is a good conductor of heat and an effective insulator, which slows down the spread of the fire. These extinguishers are effective on Class A fires, which include ordinary combustible materials like wood, paper, and cloth. Water extinguishers should not be used on electrical fires, flammable liquids, or grease fires because water can conduct electricity and may spread the fire or cause electrocution. Some types of water extinguishers include jet water extinguishers (powerful stream), water spray extinguishers (fine mist to cover larger area and reduce oxygen), and water additive extinguishers that have chemicals to improve water's effectiveness by reducing surface tension and helping it adhere to burning materials more efficiently. In summary, water extinguishers work by removing the heat from the fire triangle (heat, fuel, oxygen), mainly through cooling, to extinguish Class A fires and prevent re-ignition.
