Key Takeaways
- Fire extinguisher ratings are based on the type and size of fire they can put out.
- The letter in the rating indicates the class of fire: A for ordinary combustibles, B for flammable liquids, C for energized electrical equipment, D for combustible metals, and K for cooking oils.
- The number in the rating indicates the extinguishing potential: the higher the number, the larger the fire it can extinguish.
- Some extinguishers have multiple ratings, such as 2A:10B:C, which means they can be used on class A, B, and C fires.
- It is important to choose the right type and size of fire extinguisher for your needs and follow the instructions on how to use it safely.
What are Fire Extinguisher Ratings?
Fire extinguisher ratings are a way of measuring the effectiveness and suitability of a fire extinguisher for different types of fires. They are determined by testing the fire extinguisher according to the standards set by the Underwriters Laboratory (UL) or other recognized organizations.
The ratings consist of a letter and a number, such as 1A or 10B. The letter indicates the class of fire that the fire extinguisher can put out, while the number indicates the size of fire that it can extinguish under test conditions.
The following table summarizes the different classes of fire and their corresponding letters:
| Class | Description | Examples |
|---|---|---|
| A | Fires in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics. | Trash cans, furniture, curtains, books. |
| B | Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases. | Gasoline cans, paint cans, oil drums, propane tanks. |
| C | Fires that involve energized electrical equipment. | Computers, TVs, appliances, wiring. |
| D | Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium. | Metal shavings, powders, flakes. |
| K | Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fats). | Deep fryers, grills, stoves. |
The following table summarizes how the numbers in the ratings are calculated for class A and B fires:
| Class | Test Method | Number Meaning |
|---|---|---|
| A | Extinguishing a fire made of wood panels or wooden cribs of varying sizes. | The number represents the chemical/agent’s equivalent to gallons of water the extinguisher holds. Multiply the number by 1.25 to get the equivalent gallons of water. |
| B | Extinguishing a fire made of heptane (a flammable liquid) in a square pan of varying sizes. | The number represents the number of square feet that the fire extinguisher can cover. |
For example:
- A 2A fire extinguisher contains the equivalent of 2.5 gallons of water (2 x 1.25) and can put out a fire made of 144 pieces of wood (1.5 x 1.5 x 29 inches each).
- A 10B fire extinguisher can cover 10 square feet of a heptane fire in a pan.
Class C fires do not have a numerical rating because they are essentially class A or B fires that involve energized electrical equipment. The C rating means that the fire extinguisher is non-conductive and safe to use on electrical fires.
Class D and K fires also do not have a numerical rating because they require specialized fire extinguishers that are designed for specific types of fires.
Some fire extinguishers have multiple ratings, such as 2A:10B:C or 3A:40B:C. This means that they can be used on more than one class of fire. For example:
- A 2A:10B:C fire extinguisher contains the equivalent of 2.5 gallons of water (2 x 1.25) and can put out a class A fire made of 144 pieces of wood (1.5 x 1.5 x 29 inches each), a class B fire covering 10 square feet of heptane in a pan, or a class C fire involving energized electrical equipment.
- A 3A:40B:C fire extinguisher contains the equivalent of 3.75 gallons of water (3 x 1.25) and can put out a class A fire made of 216 pieces of wood (1.5 x 1.5 x 29 inches each), a class B fire covering 40 square feet of heptane in a pan, or a class C fire involving energized electrical equipment.
How to Choose and Use a Fire Extinguisher
Choosing the right type and size of fire extinguisher is crucial for your safety and the effectiveness of the fire extinguisher. Here are some tips to help you choose and use a fire extinguisher:
- Check the fire extinguisher ratings and labels to make sure they match the type of fire you are facing. Do not use a fire extinguisher that is not suitable for the fire class or too small for the fire size.
- Follow the instructions on the fire extinguisher label and use the PASS technique: Pull the pin, Aim the nozzle at the base of the fire, Squeeze the handle, and Sweep from side to side until the fire is out.
- Keep a safe distance from the fire and avoid inhaling the smoke or fumes. If the fire is too big, spreading, or blocking your exit, do not attempt to fight it. Call 911 and evacuate immediately.
- After using a fire extinguisher, check if the fire is completely out and dispose of the used fire extinguisher properly. Do not reuse or recharge a fire extinguisher unless it is done by a professional.
Fire extinguishers are valuable tools for preventing small fires from becoming large and dangerous. By understanding fire extinguisher ratings and choosing and using them correctly, you can protect yourself and your property from fire damage.
