Choosing the Right Fire Extinguishers

Often someone in need of a fire extinguisher will buy an ABC fire extinguisher without giving much thought to the actual fire hazards they need to protect themselves against. When shopping for fire extinguishers, you need to know several things about fire extinguishers to make an informed decision, specifically, the class of fire to protect against and any special conditions to be aware of (computer electronics, for example).

Fire extinguisher classes

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 trash can and burning firewood. These extinguishers are used to put out fires involving common fuels such as paper, cloth, rubber, and some plastics (materials that leave ash when burned, 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 put out fires involving flammable liquids such as gasoline, lubricating oil, diesel fuel, and many organic solvents found in laboratories (stuff 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 electrical plug with an outlet turned on. These extinguishers are used to extinguish electrical fires in energized electrical equipment, electric motors, circuit panels, switches, and tools (“C” for electrical current).
• 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 involving metals and metal alloys such as titanium, sodium, and magnesium.
• Class K: Class K fire extinguishers are used specifically for cooking oil and grease fires (“K” for cooking).

You can get fire extinguishers with a single class rating or multiple fire class ratings (ABC or BC, for example).

extinguishing materials

Fire extinguishers use different materials to put out fires. When choosing your extinguisher, you need to determine what type of fire you may be fighting, and then choose the best extinguishing material for your application.

• Water: Water extinguishers, or APWs, use pressurized water to extinguish fires. APW extinguishers may only be used for Class A fires (combustibles such as paper, cloth, etc.); they cannot be used to put out other classes of fires.
• Dry Chemical: Dry chemicals are used to extinguish Type A, B, C, or D fires. They work by depositing a fine layer of dry chemical on the material that is burning. Dry chemical extinguishers are very effective in putting out fires. However, dry chemical extinguishers can be abrasive and corrosive to electronics and other materials.
• Carbon Dioxide: Carbon dioxide works by removing oxygen from the immediate vicinity of the fire. Carbon dioxide extinguishers are only used for B (flammable liquid) and C (electrical fires) extinguishers. For computers, scientific and medical 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 extinguishers use metal or sand, such as sodium chloride (NaCl) or powdered copper metal, to extinguish metal and metal alloy fires.

special applications

Some fire hazards require specialized fire extinguishers. Here are some examples of those apps.

Metal or sand extinguishers are used to put out class D fires (metals and metal alloys):

• Salt (sodium chloride, NaCl) is the most commonly used material in metal/sand fire extinguishers. NaCl extinguishers work well on fires involving magnesium, sodium, potassium, potassium and sodium alloys, uranium, and powdered aluminum.
• Sodium carbonate extinguishers are also used on fires involving sodium, potassium, and sodium-potassium alloys. When considering stress corrosion of stainless steel, this type of fire extinguisher would be a better choice than a NaCl extinguisher.
• Powdered copper (Cu) metal is used for fires involving lithium and lithium alloys.
• Graphite powder extinguishers are used on lithium fires, as well as fires involving high-melting metals such as titanium and zirconium.
• Sodium bicarbonate-based extinguishers are used on fires involving metal alkyls and pyrophoric liquids.

Halotron I is a clean agent replacement for Halon 1211, the use of which was banned due to its ozone-depleting properties. Halotron I extinguishers are used to extinguish fires in computer rooms, clean rooms, and where telecommunication or electronic equipment is present. Halotron leaves no residue and is non-conductive but more expensive than carbon dioxide. It should be noted that Halotron I will no longer be produced after 2015.

FE-36 (CleanGuard) extinguishers are another clean agent replacement for Halon 1211. FE-36 extinguishers are less toxic than Halon 1211 and Halotron I and reportedly have no film depletion potential. ozone. FE-36 is also used for fires in computer rooms, clean rooms, and where telecommunications or electronic equipment is present. Unlike Halotron I, the FE-36 is not planned to be phased out.

Non-magnetic Fire Extinguishers – Whenever strong magnets are used, for example, Magnetic Resonance Imaging (MRI) or Nuclear Magnetic Resonance Spectrometers (NMRS), non-magnetic fire extinguishers should be chosen. The strong magnetic fields generated by this type of equipment can cause steel cylinder fire extinguishers to fly across a room with deadly force.

It’s important to make sure you have the right fire extinguishers for your environment or potential fire hazards. It can be the difference between whether your fire is eliminated or causes a catastrophe.