An architect told me that I don’t have to specify the weight of the fire extinguisher just the designation (2A-10BC). Is this true?
I know that what the letter designations (A, B, C, D &K) mean, but what does the numerals (2, 10, etc.) mean? Yes I did look in NFPA 10 but could not find it.
The number is a rating that indicates the relative extinguishing effectiveness. This is applicable only for Class A and B fires; Class C, Class D, and Class K fires are not required to have a numeral precede the classification letter.
While this number is related to the capacity of the extinguisher, it is not necessarily a unique one-to-one relationship. For example, for multi-purpose dry chemical extinguishers, 3-A:40-B:C is available in both 5 lb and 6 lb capacities, and there are 5 lb units with 2-A:10-B:C capacity.
So I recommend that both the capacity of the extinguisher and the number-letter designations be specified.
Thanks Dave!
What do you mean by “relative effectiveness”? Relative to what?
BTW, we used to never specify extinguishers, only cabinets. The Owner typically had a service contract with a company that supplied and maintained extinguishers. That said, the trend is towards the Owner wanting the GC to provide extinguishers as part of the construction.
Also, the new IBC has eliminated portable fire extinquishers if the building is sprinklered. The exceptions are hazardous areas such as kitchens, laboratories, etc.
Relative to other extinguishers, for size/capacity and for extinguishing agent (multi-purpose dry chemical, pressurized water, etc)
I got the following explanation from my local fire chief:
Class A Extinguishers will put out fires in ordinary combustibles, such as wood and paper. The numerical rating for this class of fire extinguisher equates to an amount of water and the amount of fire it will extinguish.
Class B Extinguishers should be used on fires involving flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire extinguisher relates to the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish.
Class C Extinguishers are suitable for use on electrically energized fires. This class of fire extinguishers does not have a numerical rating. The presence of the letter C indicates that the extinguishing agent is non-conductive.
Class D Extinguishers are designed for use on flammable metals and are often specific for the type of metal in question. These extinguishers generally have no rating nor are they given a multi-purpose rating for use on other types of fires.
David:
I thought I had already posted this, but the explanation for the numbers is the square footage (or hundreds of square feet) covered by the extinguisher. If its a type A extinguisher, the number is the 1000 square feet covered for that type of fire: a 2:A is 2000 square feet of normal combustible material. For B and C fires, its the square footage: a 10:B:C is 10 square feet of type B or type C fire. These are not CO2 or water energized extinguishers, but usually a smothering type. The various extinguisher catalogs have this information. Its how you size the thing for the space.
Anne:
I think Richard’s explanation is correct. For Type A extinguishers the numeral stands for how comperable the extinguishing capacity is to many gallons of water. For example a 2A extinguisher can put out that same amount as 2 gallons of water.