How do I calculate fire rating of extinguisher for a medium risk factory with gross floor area of 3600sqm?

Question

fire extinguisher rating e.g. 13A. How do I calculate how many fire extinguisher to put in a floor of a building, given the floor area is 3600sqm and in relation to their rating

Answer 1

Maximum travel distance can never exceed 75 feet in any situation. However, that doesn't mean the fire extinguihsers get to be every 150 feet! It's based on multiple factors:

The hazard class of the occupancy plays a big role (i.e. a factory that processes paper products is going to be a higher hazard than say a factory that produces metal parts.) These classes are broken down to Light (low hazard), Ordinary (Moderate), or Extra (High) Hazard occupancies.

The next thing we have to look at is the classification of the extinguisher you are using. It will have a UL rating, something like 4A:60B:C. The number of A units is multiplied by a square footage factor that is based on the occupancy we just talked about.

The maximum amount of square footage the extinguisher can cover, per units of A in its rating, is 3000, 1500, and 1000 respectively with the lowest square footage being for the high hazard group. Also no extinguisher can ever be allowed to cover more than 11,250 square feet.

Let's run an example...

Let's assume your factory is a moderate hazard and you are ordering 10Lb. ABC Multipurpose fire extinguishers to cover it with a rating of 4A:60B:C. Then each unit can cover roughly 6000 sq.ft. of floor space with travel distances never exceeding 75 feet.

Divide the factory up into 6000 sq.ft. "sections" where each section gets 1 fire extinguisher located somewhere inside that section. Place them where they will be safe from impact, can be seen, will not be blocked, and on paths to an exit whenever possible. Insure travel distance does not exceed 75 feet to any unit from any point in the facility and that's NOT necessarrily measured in a straight line, but along the path someone might have to take to get around equipment and what not.

Finally, you must also be aware that there are specific pieces of equipement that may also need a fire extinguisher of a particular type located within even closer distances, such a flammable dip tanks, industrial tow motor recharging areas, flammable storage areas, etc., etc.

NFPA 10 is the National Standard on placement of fire extinguishers. Almost every state in the nation adopts it as code. This guide has really good illustrations and discussed various examples to handle almost every conceiveable layout. I highly recommend getting a copy and referring to it.

Also, involve your local fire prevention officer (or fire marshal) and/or your insurance company. They may have additional items for you to consider and they will probably be more than willing to help.

Answer 2

This all depends on what type of materials you plan on having in this space. I am a fire fighter and i hope this will help you . If you are going to have materials like wood,. grass, hay or other general types of materials then you need a class A system. If you are going to house gas or oil or grease, or other flamable liquids then you need to have class B. If you are going to have electrical equipment then you need a class C. And if you plan on having metals like aluminium or others than you need a class d. Now also you can get a few mixed ones like class A,B,C or A,B. If you are going to have it as a ware hose i would suggest either a Co2 system installed, they are a bit costly but will more than do the trick and if you are not worried about a bit of a mess you can go with a hi-expansion foam. Now either of these will take care of a fire and very well, as they will both smother the fire. But as always you have to check and see what the building code in your area calls for.