Fire extinguishers may be more complex than they initially seem. Most of us are familiar with standard fires that may come from wood, paper and other solids, or even grease fires that happen in kitchens. That just scratches the surface, but thankfully you can read on to get prepared for a wider range of fires.
Fire extinguishers come in five different classes for different types of fires. Fire extinguishers will have a sticker on the side or bottom that states which class of fire they can fight. Class types are based on the fuel source for the fire:
- Class A: Flammable solids. These are the most common type of fire and they usually start on papers, woods, plastics and cloth.
- Class B: Flammable liquids and gases. When oils, paraffin wax, diesel or other liquids catch fire it is a flammable liquid fire. When gasoline vapors, propane, butane and methane catch fire it is a gas fire.
- Class C: Electrical Fires. This is any fire that involves electricity as its source. Using a non-class E extinguisher on an electrical fire can be significantly dangerous.
- Class D: Combustible metal fires. Some metals such as magnesium and aluminum can spark and start fires when they reach a certain temperature. Magnesium and many other metals cannot be extinguished with water.
- Class K: Kitchen fires. These are fires that use oils, greases and fats. Most restaurants have a special fire apparatus for their grills because standard extinguishers will not work.
Different types of extinguishers fight different types of fires. Use the class-letter stickers to determine if your extinguisher can put out a fire. Knowing the type, or what suppressant your extinguisher uses, can help you best use your fire extinguisher. The type will be clearly labeled on your extinguisher. The types are:
- Water: These are some of the most common fire extinguishers and they are used Class A fires. This type of extinguisher can be very dangerous if used on other fires, especially Class B and C.
- Foam: These extinguishers are becoming more prevalent because they can put out Class A and B fires. They are not recommended for Class C fires, but do not carry the same risk as water.
- Powder: Dry powder extinguishers are common in schools and other areas where multiple types of fires occur. These work on Class A, B and C fires. They work best for Class B. If you’re using a powder extinguisher, get as far from the fire as you can because the powder can cause harm if it gets into your eyes.
- CO2: This specialized extinguisher is designed specifically for electrical fires. They also can smother liquid fires but do not always put these fires out completely.
- Wet Chemical: This extinguisher is often not found in a hand-held unit. This material is used for grease and cooking fires and is often built into systems for large kitchens.
- Special Powder: Metal fires have their own special type of fire extinguisher. These extinguishers sometimes lack a label designating their type but they will feature a large yellow star with a “D” in the middle.
Take a P.A.S.S.
When you encounter a fire and have the proper extinguisher, use the P.A.S.S. method to put out the fire. This is the simplest way to operate an extinguisher and applies to all handheld models. P.A.S.S. stands for:
- P: Pull the pin. This unlocks the device so you can use it.
- A: Aim at the bottom. Point the nozzle at the base of the fire. This is the most effective way of putting a fire out because it targets the source.
- S: Squeeze firmly. Squeeze the handle of the extinguisher evenly and firmly.
- S: Sweep across. Sweep the base of the fire with the extinguisher’s material. Keep as far away from the fire as possible as you try to put out the fire.
| FIRE CLASS | GEOMETRIC SYMBOL | PICTOGRAM | INTENDED USE | MNEMONIC | |
|---|---|---|---|---|---|
| A | Ordinary solid combustibles | A for “Ash” | |||
| B | Flammable liquids and gases | B for “Barrel” | |||
| C | Energized electrical equipment | C for “Current” | |||
| D | (none) | Combustible metals | D for “Dynamite” | ||
| K | Oils and fats | K for “Kitchen” |