There are 5 different types of fire classes. These include:

• Class A Fires
• Class B Fires
• Class C Fires
• Class D Fires
• Class K Fires

Class A Fires – Class A fires involve ordinary combustible materials, such as, cloth, wood, paper, rubber, and many plastics. Extinguishers with an A rating are designed to extinguish fires involving these ordinary combustible materials.
Class A Fire extinguishers are used for ordinary combustibles such as rubber, wood, paper, some plastics and textiles. This fire class requires the heat-absorbing effects of water or the coating effects of certain dry chemicals. These extinguishers are identified by the letter “A.”

Class B Fires – Class B fires involve flammable and combustible liquids such as gasoline, alcohol, oil-based paints, lacquers. Therefore, extinguishers with a B rating are designed to extinguish fires involving flammable and combustible liquids.
Class B fire extinguishers are used for flammable liquid and gas fires such as oil, gasoline, etc. These fire extinguishers deprive the fire of oxygen and interrupt the fire chain by inhibiting the release of combustible vapors. These extinguishers are identified by the letter “B.”

Class C fires – class C fires involve energized electrical equipment. Extinguishers with a C rating are designed for use with fires involving energized electrical equipment.
Class C fire extinguishers are used on fires that involve live electrical equipment that require the use of electrically nonconductive extinguishing agents. Once the electrical equipment is de-energized, extinguishers for Class A or B fires may be used. These extinguishers are identified by the letter “C.”

Class D fires– Class D fires involve combustible metals, such as magnesium, titanium, and sodium. Extinguishers with a D rating are designed to extinguish fires involving combustible metals.
Class D fire extinguishers are used on combustible metals such as magnesium, titanium, sodium, etc., which require an extinguishing medium that does not react with the burning metal. These extinguishers are identified by the letter “D.”

Class K fires– Class K fires involve vegetable oils, animal oils, or fats in cooking appliances. Extinguishers with a K rating are designed to extinguish fires involving vegetable oils, animal oils, or fats utilized in commercial cooking appliances.
Class K fire extinguishers are used on fires involving cooking media (fats, grease and oils) in commercial kitchens. Due to the higher heating rates of vegetable oils in commercial cooking appliances. These fire extinguishers work on the principle of saponification, which takes place when alkaline mixtures such as potassium acetate, potassium citrate or potassium carbonate are applied to burning cooking oil or fat. The alkaline mixture combined with the fatty acid creates a soapy foam on the surface that holds in the vapors and steam and extinguishes the fire. These extinguishers are identified by the letter “K.”