By PAR002_123
•
31 May, 2019
Fire extinguishers are designed to tackle different types of fire. In this article, we look at how fire extinguishers work, discussing also how fires burn, types of fire extinguishers available and the classes of fire. The Fire Triangle A fire burns when fuel, oxygen and heat are present. These three elements form what is widely known and referred to as the fire triangle. The fire triangle can only be broken and the fire extinguished when at least one of the elements is removed. Fuel: any type of combustible material such as paper, oils, wood, gases, fabrics, liquids, plastic, rubber and more. The fuel for a fire is often categorised by its size, shape, moisture content, how easily it will burn and the temperature at which it burns. Heat: heat must also present for ignition to take place. Flammable vapours from the fuel source combust when the heat is present. Oxygen: in addition to fuel and heat, fires also need oxygen to stay alight. When the fuel burns, it reacts with oxygen to release heat and generate combustion. Types of Fire Extinguishers Fire extinguishers work by removing heat, air, or both. There are three different types of fire extinguishers available containing different chemicals. Water Extinguishers – water is the most familiar and commonly used extinguishing material and is in many cases (although not all) the most effective. Water fire extinguishers have a tank full of water with compressed air as the propellant. They work by removing heat from the fire and can put out burning materials such as wood, paper and cardboard – they aren’t as effective with electrical fire or fires involving inflammable liquids. Dry Powder Extinguishers – dry chemical extinguishers work by smothering the fire; as the layer of power smothers the fire, the oxygen is starved and the fire goes out. Carbon Dioxide Extinguishers – these extinguishers feature a mixture of liquid and gaseous carbon dioxide (a non-flammable gas) which has to be stored under high pressure to create a liquid. The C02 replaces the oxygen surrounding the fire with carbon dioxide meaning the fire can no longer burn. How Fire Extinguishers Work Fire extinguishers contain compressed air and a suppressant. When the safety pin is pulled and the operating lever is depressed, the container of compressed air inside the extinguisher is punctured and the released air rushes out into the extinguisher forcing the material up the siphon and out of the nozzle with considerable force. When using a fire extinguisher, the nozzle should be aimed directly at the fuel, rather than the flames themselves. Spraying directly on the flames will fan them rather than extinguish them. Classes of Fire Class A Fires are fuelled by combustible materials such as wood, paper, plastics, textiles and furniture. Class B Fires are fuelled by flammable liquids such as oil, paraffin or petrol. Class C Fires are fuelled by flammable gases such as hydrogen, butane, propane or methane. Class D Fires are fuelled by combustible metals such as magnesium, aluminium or potassium. Electrical Fires are fuelled by electrical appliances. Class F Fires are fuelled by cooking fats or oils (typically from chip-pans). Fire extinguishers should only be used if you are trained or feel it is safe to do so. Fire Extinguishers - Phoenix Fire Store Fire Extinguisher ID Signs - Phoenix Fire Store