FAQ About Fire Extinguishers

What are the different classifications for fire extinguishers?

The classification of fire extinguishers is based on a lettering system that indicates the types of fires on which an extinguisher has been found to be most effective. (NFPA 10 5.2)

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

Class B refers to fires in flammable liquids and gas fires such as oil, gasoline, etc. These fire extinguishers deprive the fire of oxygen and interrupt the fire chain by inhibiting the release of combustible vapors.

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

Class D fires are fires in combustible metals extinguisher such as magnesium, titanium, sodium, lithium, potassium and zirconium.

Class K fire extinguisher is used on fires involving cooking media (fats, grease, and oils) in commercial cooking such as restaurants.

How do you determine how many fire extinguishers are needed for a particular area?

Portable extinguishers should be located where they are visibly accessible in case of a fire. NFPA 10, 6.1.3.

Extinguishers weighing 40 lbs. or less should be installed so that the top of the extinguisher is no more than 5 feet above the floor. For those weighing more than 40 lbs., the top of the extinguisher should not be more than 3.5 feet above the floor. In both cases the distance between the bottom of the extinguisher and the floor can never be less than 4 inches.

Placement is dependent on the area being covered, the size of the extinguisher, and the hazard classification for the area being covered. Some local requirements may be more strict, so you should always check with your local fire marshal.

Fire Class Travel Distance*
Class A** 75 feet or less
Class B 50 feet
Class C Based on appropriate A or B hazard
Class D 75 feet

*Travel distance is the actual distance an individual needs to walk to reach the fire extinguisher and must take into account the effect of doorways, partitions or other obstacles.

** Uniformly spaced standpipe systems or hose stations can be used in place of up to ½ of the required portable fire extinguishers. The location of hose stations and fire extinguishers shall be such that the hose stations do not replace more than every other fire extinguisher. NFPA 10,

How often should my fire extinguishers be checked?

Monthly – Ensure that the fire extinguisher is in the designated location with no obstructions to access or visibility.  Also check the pressure gauge and verify that it is in the operable range.

Annually – A thorough examination of the basic elements of the fire extinguisher performed by a trained professional who has undergone the necessary instructions and has all service manuals.

What is the annual maintenance procedure for a fire extinguisher?

  • Locate the fire extinguisher and determine the accessibility and visibility. No obstructions can be present. Check for stability, height, and appropriate Class for potential hazards.
  • Remove the fire extinguisher and check hydrostatic test date, six year maintenance date (dry chemical) and condition of the cylinder and band. All instructions shall be legible and face outward.
  • Weigh the cylinder and check the gauge.  Also remove the safety pin and tamper seal. Inspect handles and then reinsert the safety pin with a new seal.
  • Remove hose, horn, or nozzle. Check for obstructions, wear, and proper operation. Reassemble.
  • A conductivity test shall be performed on carbon dioxide hose assemblies.  Replace as necessary.
  • Clean all equipment, replace worn labels and attach new annual NFPA-10 inspection tag.
  • Reinstall fire extinguisher back on the bracket.
  • If an inspection reveals that tampering has occurred or the unit is due for extended maintenance, the unit must be taken out of service. A spare fire extinguisher of equal or greater rating shall be installed while service is performed.


What is a hydrostatic test and how often is it performed?

  • Pressure testing of a fire extinguisher to confirm its strength against unwanted rupture performed by a trained professional to requalify cylinders.
  • Dry Chemical 12 years
  • Water, AFF, FFFP 5 years
  • Halogenated Agent 12 years
  • Carbon Dioxide 5 years


What is a six year maintenance?

Internal examination of an emptied dry chemical fire extinguisher.  The examination will check for corrosion and interior problems. Extinguishers passing the six year maintenance are then recharged, reassembled, and receive a six year service label and a verification of service collar.



Resources:  NFPA 10 Standard for Portable Fire Extinguishers, OSHA Standard on Portable Fire Extinguishers 29 CFR 1910.157, Lab Safety Supply – EZ Facts Safety Info – Document #135 Use, Placement, Maintenance and Testing of Portable Fire Extinguishers