Understanding fire extinguisher size involves interpreting the numbers and letters printed on the label, which indicate the type of fire it can fight and its effectiveness rating.
Fire extinguisher size is indicated by a number preceding the letter class rating (e.g., 2A:10B). These ratings are standardized and provide crucial information about the extinguisher's capacity and range.
Understanding Class A Ratings
The number before the 'A' rating signifies the extinguisher's equivalent effectiveness compared to water.
- Each number represents 1 ¼ gallons of water.
- For instance, a 2A rating means the extinguisher is just as effective as 2 ½ gallons of water (2 * 1.25 gallons = 2.5 gallons).
- A 4A rating is equivalent to 5 gallons of water (4 * 1.25 gallons = 5 gallons).
This rating helps you gauge how well the extinguisher can handle fires involving ordinary combustibles like wood, paper, and cloth. A higher number indicates a greater fire-fighting capability for Class A fires.
Understanding Class B Ratings
The number before the 'B' rating indicates the approximate square footage of a flammable liquid fire that a non-expert user should be able to extinguish.
- The Class B size rating indicates the square footage the extinguisher can cover.
- For example, a 10B rating suggests the extinguisher can effectively handle a flammable liquid fire covering about 10 square feet.
This rating is essential for fires involving flammable liquids and gases, such as gasoline, oil, or paint.
Combined Ratings
Many extinguishers are designed to fight multiple types of fires and will have combined ratings, such as 2A:10B:C.
- 2A: Effective against Class A fires equivalent to 2.5 gallons of water.
- 10B: Effective against Class B fires covering approximately 10 square feet.
- C: Suitable for use on electrical fires (the 'C' rating does not have a numerical size rating, as the effectiveness is related to the non-conductivity of the agent).
Examples of Ratings
Here's a simplified look at how ratings translate:
| Rating | Class A Equivalent Effectiveness | Class B Effective Square Footage |
|---|---|---|
| 1A | 1.25 gallons of water | N/A |
| 2A | 2.5 gallons of water | N/A |
| 4A | 5 gallons of water | N/A |
| 10B | N/A | 10 sq ft |
| 20B | N/A | 20 sq ft |
| 2A:10B | 2.5 gallons of water | 10 sq ft |
Choosing the right size depends on the potential fire hazards in the area the extinguisher will cover. Larger ratings are suitable for larger or higher-risk areas.
