Ever Admire the Fire Extinguisher?

Hand holding a fire extinguisher

We walk by fire extinguishers daily and probably don’t give them much thought.   If the time ever comes that we need an extinguisher, it would be great to know where it is and what its capabilities are. OSHA’s 1910.157 standard applies to the placement, use, maintenance, and testing of portable fire extinguishers provided for employee use. 

Where employers provide fire extinguishers, OSHA has some general employer requirements: 1910.157(c)(1)

  1. Mount, locate, and identify portable fire extinguishers
  2. Make them readily accessible
  3. Provide only approved portable fire extinguishers
  4. Assure extinguishers are maintained in a fully charged and operable condition
  5. Kept in designated places

Fire Extinguisher Classes:

Not all materials burn the same way and thus must be extinguished using the right equipment. According to NFPA and OSHA, there are five primary classes of fire:

  1. Class A: ordinary combustible materials, including wood, cloth, paper, and many plastics.
  2. Class B: flammable and combustible liquids, petroleum greases, oils, alcohols, and flammable gases.Classes of Fire
  3. Class C: energized electrical equipment is involved.
  4. Class D: combustible metal powders, flakes, shavings, or similarly sized materials. (magnesium, titanium, zirconium, sodium, lithium, and potassium)
  5. Class K: combustible cooking media (vegetable or animal oils and fats)

Some extinguisher classes can be identified based on their design; however, every extinguisher must have a nationally recognized label identifying the extinguisher class. Look for these symbols:

Fire Extinguisher Ratings:

All the OSHA and National Fire Protection Association (NFPA) safety requirements use specific ratings when referring to both Class-A and Class-B extinguishers:

  1. The A rating is a water equivalency rating. Each A is equivalent to 1-1/4 gallons of water. For example, a 4A rating = 5 gallons of water.
  2. The B rating is equivalent to the square footage of a burning flammable liquid that the extinguisher can cover when handled by a professional. 20 B:C = 20 square feet of coverage.
  3. The C rating indicates it is suitable for use on electrically energized equipment.


Pound Rating


B:C Rating

Emptying Time

2.5 lbs.



10 seconds

4 lbs.



12-15 seconds

5 lbs.



15-20 seconds

10 lbs.



30 seconds

20 lbs.



60 seconds


Fire Extinguisher Placement:

When extinguishers are located in the workplace, there are some key installation details that need to be controlled.  1910.157(c)(1) requires the employer to mount, locate, and identify them so that they are readily accessible to employees without subjecting the employees to possible injury.  Below are a few key things employers should be aware of:

  1. Class A environment = travel distance 75 feet or less (OSHA 1910.157(d)(2) and NFPA 906.3.1).*


    Light (Low) Hazard Occupancy

    Ordinary (Moderate) Hazard Occupancy

    Extra (High) Hazard Occupancy

    Minimum rated single extinguisher





  2. Class B environment = travel distance 30 to 50 feet depending on size of extinguisher (OSHA 1910.157(d)(4) and NFPA 906.3.1).





    Light (Low) - Small amounts of flammable liquids, offices, churches, assembly halls, classrooms, and hotel guest areas, etc.




    30 feet


    50 feet

    Ordinary (Moderate) – Greater amount of flammable liquids than low-hazard locations. Garages, workshops, support service areas, light manufacturing, dining areas, auto showrooms, parking garages and storage areas, etc.




    30 feet


    50 feet

    Extra (High) - Flammable liquids are present and used in large quantities. Areas used for storage, production, woodworking (finishing), vehicle repair, aircraft and boat servicing, or where painting, dipping, and coating, operations are performed with flammable liquids.




    30 feet


    50 feet


  3. Class D environment = Travel distance less than 75 feet from flammable metal.
  4. Class K environment = Travel distance 30 feet or less from hazard area.
  5. Hot work activities = Travel distance 25-feet or less.
  6. Areas under construction = Structures under construction, alteration, or demolition shall contain at least one extinguisher in accordance with NFPA 3351.1, Section 906.
    1. At each stairway on all levels where combustible materials have accumulated.
    2. In every storage and construction shed.
    3. Additional extinguishers shall be provided where specific hazards exist.
  7. Motor fuel pump, dispensers, and tank fill openings = Travel distance 75-feet or less. (NFPA Chapter 23, section 2305.5)
  8. Storage and dispensing of flammable and combustible liquids on farms and construction sites Must be in clear view and travel distance less than 50 feet of the storage tank. (NFPA Chapter 61, section 6108.2)
  9. Fire extinguishers shall be located in designated locations.
  10. To mount extinguishers to avoid injury they should be hung to meet both NFPA and OSHA regulations.Fire Extinguisher
    1. When wall mounted, fire extinguishers shall have at least 4-inches of clearance from the bottom to the floor.
    2. Extinguishers 40-pounds and under mounted less than 5’ high.
    3. Extinguishers 40-pounds and over mounted less than 3.5’ high.
    4. American Disability Act (ADA) guidelines prohibit extinguishers from protruding more than 4-inches into walkways, corridors, passageways, or aisles.
  11. Once the extinguisher has been mounted, the employer shall identify extinguishers and their designated locations so that they are readily accessible to employees.There is no specific regulation for the method of identification, so posting a sign, painting a mark above extinguisher, or marking the roof support column the extinguisher is attached to will meet the requirement.

*NOTE for Class A Environments: Uniformly spaced standpipe systems or hose stations connected to a sprinkler system for emergency use can be used instead of Class A portable fire extinguishers, if they meet the respective requirements of OSHA 1910.158 and 1910.159, provide total coverage of the area to be protected, and employees shall be trained at least annually in their use. (1910.157(d)(3))