Fires can happen anywhere, but lab fires can be even more dangerous due to Bunsen burners, flammable liquids, research documents, laptops and lab equipment that might be present at any given time. Due to these unique circumstances, it’s important that every lab be prepared with the correct fire extinguisher, inspection requirements and training.

OSHA regulation 29 CFR 1910.157 governs the requirements for portable fire extinguishers. Testing and approval for fire extinguishers is done by FM Global (FM) and listed by Underwriters' Laboratories, Inc. (UL).

Fire extinguishers are classified by the types of fires they put out.

  • Class A is for combustibles such as wood, paper, some plastics and textiles.
  • Class B is for flammable liquids.
  • Class C is for electrically conductive fires.
  • Class D fire extinguishers are for flammable solids such as magnesium, sodium or titanium.
  • Class K fire extinguishers are specific to commercial kitchen applications.

Many fire extinguishers are sold as ABC fire extinguishers that put out all three classes of combustibles, flammable liquids and electrically conductive fires.

After fire extinguishers are listed by UL, they are given a UL rating, such as 4A:20B:C. The A rating is a water equivalency rating. Each A is equivalent to 1.25 gal. of water. 4A=5 gal. of water. The B:C rating is equivalent to the amount of square footage that, related to the degree of training and experience of the operator, the extinguisher can cover. 20 B:C=20 sq. ft. of coverage.

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. Employers must give employees fire extinguisher training when they are hired and re-train annually. Fire extinguishers must be inspected monthly per OSHA standard1910.157 (e)(2).

For more detailed information on fire extinguisher inspection requirements and standards, read Use, Placement, Maintenance and Testing of Portable Fire Extinguishers: EZ Facts No. 135.

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