Class A Fires are fires that use ordinary combustibles as their fuel. If items such as wood, paper, cloth, rubber, some plastics, and/or trash combust, it is considered class A. Class A fires are the most common and usually the easiest to contain. They also are classified by their ability to produce ash. Class A fires can be controlled by using either water, foam, halotron, or any dry chemical extinguishers.
Class B Fires are fires that involve flammable liquids and gases. Gasoline, paint, paint thinner, propane, butane, kerosene, acetylene, lacquer, oil based liquids, and alcohol are all considered class B fire fuels. Class B fires can be controlled with either foam, halotron, dry chemical, or CO2 extinguishers. Water should never be used on this type of fire. It will only cause the fuel to splash and possibly spread.
Class C Fires are fires that involve energized electrical wiring and equipment. Class C fires are unique because as soon as the the electricity is cut or dies, it becomes one of the other fire classes. Once again water should not be used to control this type of fire. Since water can carry a current, the risk of electrocution is eminent. Class C fires can be controlled with CO2, Halotron, and dry chemical fire extinguishers.
Class D Fires are fires that involve combustible metals like magnesium, potassium, aluminum, titanium, and sodium. Most of these metals will typically burn at higher temperatures and can react violently with water or other chemical agents. According to the NFPA, “Class D fires can be controlled with dry powder extinguishing agents based on sodium chloride or other salts; also clean dry sand”. Dry powder should not be confused with dry chemical. Trying to extinguish a metal fire with a dry chemical extinguisher will only result in spreading the fire. Simply put, this is a job for a fire professional.
Class K Fires are fires involve cooking & vegetable oils, grease, and fats. It can be considered a sub category of a class B fire but since they typically burn at higher temperatures they have been given their own distinction. Class K fires can be controlled with either a wet or dry chemical extinguisher. These types of chemical extinguishers can quickly change the burning oils into a non-combustible soap through saponification.