Many fire extinguishers contain chemicals for putting out combination fires; in fact, extinguishers classed B:C and even ARC are more widely available for home use than extinguishers designed only for individual types of fires. All-purpose ARC extinguishers usually are the best choice for any household location; however, B:C Fire Extinguishers Crewe put out grease fires more effectively (their charge of sodium bicarbonate reacts with fats and cooking oil to form a wet foam that smothers the fire) and so should be the first choice in a kitchen.
“Rating” is a measurement of a fire extinguisher’s effectiveness on a given type of fire. The higher the rating, the more effective the extinguisher is against the class of fire to which the rating is assigned. Actually, the rating system is a bit more complicated: rating numbers assigned to a Class A extinguisher indicate the approximate gallons of water needed to match the extinguisher’s capacity (for example, a 1A rating indicates that the extinguisher functions as well as about a gallon of water), while numbers assigned to Class B extinguishers indicate the approximate square footage of fire that can be extinguished by an average nonprofessional user. Class C extinguishers carry no ratings.
Often, someone who needs a fire extinguisher will buy an ABC fire extinguisher without giving much thought to the actual fire hazards they need to protect against. When buying fire extinguishers, you need to know several things about extinguishers in order to make an informed decision, specifically, the fire class you need to protect against and special conditions you need to consider (computer electronics, for example).
Classes of fire extinguishers
When it comes to fire extinguishers, there are five classes of fires: A, B, C, D, and K.
Class A – Fire extinguishers rated for Class A fires have a green triangle with an “A” in the center as well as a pictogram of a garbage can and wood burning. These extinguishers are used to put out fires for common combustibles like paper, cloth, rubber, and some plastics (materials that leave ash when burnt, hence, the “A”).
Class B – Fire extinguishers rated for Class B fires have a red square with a “B” in the center as well as a pictogram of a gasoline can with a burning puddle. These extinguishers are used to extinguish fires for flammable liquids like gasoline, lubricating oil, diesel fuel, and many organic solvents found in laboratories (things found in barrels, hence “B”).
Class C – Fire extinguishers rated for Class C fires have a blue circle with a “C” in the center as well as a pictogram of an electric plug with a burning outlet. These extinguishers are used to extinguish electrical fires for energized electrical equipment, electric motors, circuit panels, switches, and tools (“C” for current-electrical).
Class D – Fire extinguishers rated for Class D fires have a yellow pentagram (star) with a “D” in the center as well as a pictogram of a burning gear and bearing. These extinguishers are used to extinguish fires from metals and metal alloys like titanium, sodium, and magnesium.
Class K – Class K fire extinguishers are used specifically for cooking fires from grease, fat, and cooking oil (“K” for kitchen).
You can get fire extinguishers with a single class rating or multiple fire class ratings (ABC or BC, for example).
Fire extinguishing materials
Carbon dioxide: Carbon dioxide works by removing oxygen from the immediate vicinity of the fire. Carbon dioxide extinguishers are only ever used for B (flammable liquid) and C (electrical fires) extinguishers. For computer, medical and scientific equipment, and aircraft electronics, carbon dioxide would be a better choice than dry chemical extinguishers because a carbon dioxide extinguisher leaves no residue.
Metal/sand: Some class D fire extinguishers use metal or sand, such as sodium chloride (NaCl) or powdered copper metal, to smother fires from metals and metal alloys.
Some fire hazards require specialized extinguishers. Here are a few examples of those applications.