Almost all fires are small in their incipient stage and can be put out quickly if the proper firefighting equipment is available and the person discovering the fire has been trained to use the equipment at hand. Most facilities turn to portable fire extinguishers for fighting incipient stage fires. The requirements for portable fire extinguishers in general industry are governed by the Occupational Safety and Health Administration (OSHA) and are located in 29 Code of Federal Regulations (CFR) 1910.157.

To be effective, according to OSHA, portable fire extinguishers must be:

  1. Approved by a recognized testing laboratory and listed by Underwriters’ Laboratories, Inc. (UL)
  2. Of the proper type for the class of fire expected
  3. Located where they are readily accessible for immediate use and in sufficient quantity and size to deal with the expected fire
  4. Inspected and maintained on a regular basis so that they are kept in good operating condition
  5. Operated by trained personnel who can use them effectively

Classification and Use

Underwriters’ Laboratories classifies fire extinguishers by the type of fire that they will extinguish.

Class A fire extinguishers are used for ordinary combustibles such as wood, paper, some plastics and textiles.

Class B fire extinguishers are used for flammable liquid and gas fires such as oil, gasoline, etc.

Class C fire extinguishers are used on fires that involve live electrical equipment that require the use of electrically nonconductive extinguishing agents.

Class D fire extinguishers are used on combustible metals such as magnesium, titanium, sodium, etc., that require an extinguishing medium that does not react with the burning metal.

Class K fire extinguishers are used on fires involving cooking media (fats, grease and oils) in commercial kitchens.


Portable fire extinguishers are labeled so users can quickly identify the classes of fire on which the extinguisher will be effective. The marking system combines classification pictographs and operation instructions on a single identification label.

Also located on the fire extinguisher label is the UL rating, which is broken down by the classes of fire on which an extinguisher would be effective. Numerical ratings allow you to compare the relative extinguishing effectiveness of various fire extinguishers. For example, an extinguisher that is rated4A:20B:C indicates the following:

  1. The A rating is a water equivalency rating. Each unit of A is equivalent to the effectiveness of 1.25 gallons of water. 4A = 5 gallons of water.
  2. The B rating is equivalent to the square footage of a burning liquid the extinguisher can cover, related to the degree of training and experience of the operator. 20 B:C = 20 square feet.
  3. A C rating carries no numerical value.  It simply indicates it is suitable for use on electrically energized equipment.


OSHA requires employers to select and distribute fire extinguishers based on the classes of anticipated workplace fires and also on the size and degree of the hazard, which would affect their use.  The requirements for placement are mostly based on the square footage of floor area per extinguisher and the distance one might have to travel to reach an extinguisher.


Where the employer has provided fire extinguishers for employee use, the employer must provide an educational program to familiarize employees on the principles and use of the extinguishers. This educational program should be completed during the initial hiring and annually thereafter.

Maintenance, Inspection and Testing

Employers must inspect, maintain and test all portable fire extinguishers in accordance with 29 CFR 1910.157(e) and (f).

Visual Inspection: Portable fire extinguishers must be visually inspected monthly per 29 CFR 1910.157(e)(2). The inspection should assure that:

  1. Fire extinguishers are in their assigned place
  2. Fire extinguishers are not blocked or hidden
  3. Fire extinguishers are mounted in accordance with NFPA 10
  4. Pressure gauges show adequate pressure; carbon dioxide (CO2) extinguishers must be weighed to determine if leakage has occurred
  5. Pin and seals are in place
  6. Fire extinguishers show no visual sign of damage or abuse
  7. Nozzles are free of blockage

Maintenance Requirements: The maintenance requirements depend on the type of portable fire extinguisher. Stored pressure dry chemical type extinguishers, for example, require a thorough external maintenance by a trained professional each year. Dry chemical extinguishers that require a 12-year hydrostatic test are required to be emptied and subjected to applicable maintenance procedures every six years.

Hydrostatic testing: Hydrostatic testing of portable fire extinguishers is done to help protect against unexpected in-service failure. This can be caused by internal corrosion, external corrosion and damage from abuse, etc. Hydrostatic testing must be performed by trained personnel with proper test equipment and facilities.

For each extinguisher that is hydrostatically tested, the employer must keep a record that includes:

  • The name of the person or company that performed the last hydrostatic test, and the test date
  • The signature of the person who performed the test
  • The serial number or other identifier of the fire extinguisher that was tested

This information should also be securely affixed to the tested extinguisher. These records must be kept until the extinguisher is hydrostatically re-tested or until the extinguisher is taken out of service, whichever comes first.

At Albany Fire Extinguisher, we offer an array of solutions to keep commercial buildings safe. Our trained technicians will work with you to determine which equipment and maintenance plan is best for your business, and we will also install and maintain the equipment for your commercial building.