Within the world of firefighting, fire is classified under five classes. This gives a better system of understanding the many types of fire that fire personnel face each day. Each class of fire is fought differently and requires a different tactic and strategy for controlling it.
Each classification of fire is listed under wither an A class, B class, C class, D class, or K class. In the United Kingdom, Class k fires are also known as Class F.
Class A fires are the fires that are more common in today’s world of firefighting. These fires are caused by combustible materials such as wood. More commonly known fires in this class are candle fires, campfires, fires resulting from a match ignition, and also lighter ignitions. A fire triangle is what causes these fires to remain hot and consist of heat, oxygen, and a fuel source.
A Class A fire requires all three to be at the right consistency or a fire can not continue. When the material becomes hot enough to cause combustion or an open flame usually caused by a match or lighter, then the fire spreads to other materials around it. Oxygen is available to the flames and allows it to grow more and more dangerous.
Campfires are usually a contained fire but with the right ingredients such as a wind gust and surrounding brush, will leave the confines of the area and can spread through the forest at a fast rate. Firefighters know that with a Class A fire; the simplest way to put it out is by removing the oxygen and heat from the fire. Water is the common ingredient that does both. Some of the time a fire of this nature can be put out by using a chemical that will ultimately smother the fire.
Class B fires fall under the same fire triangle but gasoline and the like are the choice of fuel and not a wood product. Class B fires do not require the use of water and need a foam or CO2 based product to extinguish it. The K Class or F class as known to the United Kingdom is really a subheading under the B Class of fires. This class deals with the use of cooking oils as a source. Fire specially designed fire extinguishers are used for this. Class C fires are fires caused by electrical devices such as defective appliances. The fire triangle in this classification is fueled by the electrical current applied to it.
Water can not be used under any circumstances because the firefighters are at risk of electrocution. Many firefighters have been killed by this type of fire and the electricity traveling up the path of the water to the hose. To fight a Class C fire, the oxygen part of the fire triangle must be cut off. Firefighters use foam consisting of protein and by removing the source of electricity from the fire. Fire extinguishers have been developed to also combat this class of fire.
Class D fires are known as fires dealing with metals. These metals may be in the form of magnesium, calcium, uranium, potassium, sodium, titanium, and plutonium. These metals themselves are not the main cause of the ignition but Class A fire is ignited causing the wood around it to heat to the metal. Magnesium and other metals are known to be very hot and can become as hot as 1200 degrees.
Under no circumstances can these fires because the water will actually make the fire hotter. Dry powder is used to extinguish Class D fires and to smother the source of oxygen to the fire.