What does the UL rating for a fire extinguisher indicate?

In short, the UL rating indicates the fire type and approximate size fire the extinguisher is rated for.

The letters indicate fire type and number, if present (usually for type A and B) indicate fire size. Any number associated with the letter B is based on approximate square footage. The number with A is a bit more technical, but suffice it to say, that a 2A extinguisher has twice the extinguishing potential as a 1A.

Letters are as follows:

A - Suitable to extinguish Class A Fires, involving wood, paper, trash, etc...

B - Suitable to extinguish Class B Fires, involving flammable liquids and even gases,

C - Suitable for extinguish Class C Fires, or fires involving energized electrical equipment.

D - Suitable for Class D fires, or fires involving flammable metals.

K - Suitable for Kitchen releated grease fires (and has a compatibility with fixed fire suppression systems for kitchen hoods.)

For more information about the different types and classifications of fire extinguishers, try the following link...

Yeah. I am not even sure who put it together, but it's pretty informative. Thanks for the 10 points. Report It

Class A and B fire extinguishers have a numerical rating based on tests conducted by UL (Underwriter鈥檚 Laboratories). The UL rating is broken down into Class A and Class B:C ratings. These numerical ratings allow you to compare the relative extinguishing effectiveness of various fire extinguishers.

For example, an extinguisher that is rated 4A:20B:C indicates the following:

The A rating is a water equivalency rating. Each A is equivalent to 1-1/4 gallons of water. 4A=5 gal. of water.
The B:C rating is equivalent to the area (square footage) that, related to the degree of training and experience of the operator, the extinguisher can cover. 20 B:C=20 square feet of coverage.
C indicates it is suitable for use on electrically energized equipment.
When analyzing these ratings, note that there is not a numerical rating for Class C or Class D fires. Class C fires are essentially either a Class A or Class B fire involving energized electrical equipment where the fire extinguishing material must be nonconductive. The fire extinguisher for a Class C fire should be based on the amount of the Class A or Class B component. For extinguisher use on a Class D fire, the relative effectiveness is detailed on the extinguisher nameplate.