Fire Extinguisher ABCs

Rating

Fire extinguisher ratings appear as a series of letters and numbers (e.g., 2A10BC). The letters indicate the class of fire the extinguishing agent is designed for. Depending on which letter they precede, the numbers can indicate either the approximate relative extinguishing potential or the size of fire that can be put out by a trained operator using that extinguisher.

The most reliable rating is that assigned by UL (Underwriters Laboratories—an independent entity that tests consumer products according to governmental safety standards), which appears on the equipment nameplate. Size alone is not a good measure of extinguisher effectiveness. (Although generally speaking, the larger the extinguisher, the longer the spray time.) The efficiency of non-rated, “general purpose” extinguishers is difficult to judge.

The Letters

Different types of fires require different extinguishing agents. Manufacturers choose the right extinguishing agent (e.g., carbon dioxide, dry chemical, or foam) for each fire classification. Your job as a consumer is to know what type of fire you want protection against and choose an extinguisher designed to be effective against that type of fire. You do this via fire classifications—the letter (A, B and/or C) that appears in the rating.

Class A fires are the most common type, involving ordinary combustibles such as wood, paper, cloth, rubber, and plastics.

Class B fires involve flammable liquids (such as gasoline, kerosene, oil), gases, and greases.

Class C fires involve electrical appliances, equipment, or wiring, where the electrical nonconductivity of the extinguishing agent is important (i.e., when there is risk of getting electrocuted). Note: when the equipment or wiring is de-energized (unplugged, not live), remaining combustion is Class A or B, and extinguishers designed for those fires may be safely used.

The Numbers

The number preceding Class A indicates the approximate relative extinguishing potential. This number relates to the square feet of ordinary combustible material the extinguisher can put out and is dependent on the type of extinguisher as well as the efficiency of design and use.

The number used for Class B indicates the square footage of a deep-layer flammable liquid fire that a trained operator can put out.

Choice and Placement

Your choice of extinguisher should be based on potential use. For instance, oil, grease, and electrical fires are likely in the kitchen, garage, and car, so the obvious choice would be a BC extinguisher. However, much can be said for being prepared for any situation, so unless the application is specific, choose the most versatile extinguisher with the largest capacity that can be easily handled by potential users. For home use it may be best to go with a heavy-duty rated, multipurpose (ABC) dry-chemical fire extinguisher.

The National Fire Protection Association recommends you have at least one extinguisher for every 600 square feet of living area. Fire extinguishers should be located on every level of the home—the kitchen, garage, and basement should each have its own fire extinguisher. Do not mount extinguishers too close to the location where a fire might occur—the user should not risk reaching into a fire or going into a burning area to get a fire extinguisher.

Use

Remember these steps for effective fire extinguisher use:

We’d add one more item to the top of this list: keep your cool. Easier said than done, but invaluable. 

NOTE: Fight only minor fires. In case of a serious blaze, leave the building immediately and notify the fire department from your cell phone, a neighbor’s home, or an alarm box.

Maintenance

Choose and install fire extinguishers that have a gauge, and check the gauge once a month. If the gauge reading is low, promptly bring it to a professional (search for “fire extinguisher service” online or look in the yellow pages) to have it recharged (filled or pressurized). Be sure to have your extinguisher recharged after each use.