Sizing Fire Extinguishers

Q: I can find a lot of information about portable fire extinguishers but nowhere can I find what size is required for use in a hospital. Can you point me in the right direction? We specified 2.5 lbs. and 5 lbs. and no one can tell me what is correct.

A: Section of the 2012 Life Safety Code says portable fire extinguishers must be selected, installed, inspected, and maintained in accordance with NFPA 10. NFPA 10-2010, section 5.1 says the selection of fire extinguishers for a given situation shall be determined by the applicable requirements of Sections 5.2 through 5.6 and the following factors:

  1. Type of fire most likely to occur
  2. Size of fire most likely to occur
  3. Hazards in the area where the fire is most likely to occur
  4. Energized electrical equipment in the vicinity of the fire
  5. Ambient temperature conditions
  6. Other factors

So, you must first determine the classification of the potential fire (Class A, Class B, Class C, or Class K) and then place an appropriate fire extinguisher nearby. How far away from the potential fire is determined on the capacity of the fire extinguisher and the hazard of the potential fire.

For example, Table identifies the fire extinguisher size and placement for Class A hazards. The hazards are listed as Light, Ordinary, and Extra and the selection of the capacity of the fire extinguisher is dependent on the level of hazard and the area served by the extinguisher. For a fire extinguisher that has a capacity of 2-A, the maximum floor area of light hazard (most areas of hospitals are light hazard, other than Laboratories, Pharmacies, Central Storage, Boiler rooms, etc.), it can serve up to 6,000 square feet (3,000 sq. ft. for each unit of ‘A’… 2-A = 6,000 sq. ft.), and the maximum travel distance to get to a Class A extinguisher is 75 feet.

But be careful… as the level of hazard goes up, the area served by the same size extinguisher goes down. Even though they may have the same travel distance to get to an extinguisher (75 feet), the total area served by the extinguisher is reduced. Similarly, Class B, Class C, and Class K have their design limitations as well. You will note that the travel distance for a Class B extinguisher is either 30 feet or 50 feet, depending on the level of hazard and the capacity of the extinguisher. Also, all Class K extinguisher have a maximum travel distance of 30 feet.