Standards Matter

Fire Extinguisher Standards: Helping to Contain and Put Out Small Fires

UL Standards & Engagement
December 6, 2021

Various types of fire extinguishers isolated on white background.

Why it matters

In any fire event, the first priority is to escape the fire safely. However, if the fire is small and confined, it may be appropriate to use a fire extinguisher. Fire extinguishers come in multiple shapes, sizes, ratings, and classifications based on the types of fires they are intended to attack. These attributes are critical in determining how a fire extinguisher will perform against any particular fire. 

What we’re doing

By specifying the requirements of ratings and performance during fire tests, UL 711/ULC-S508, the Standard for the Rating and Fire Testing of Fire Extinguishers, helps to ensure the different classes of fire extinguishers are suitable for attacking specific types of fires. The Standard covers fire extinguishers intended to attack Class A, B, C, D, and K fires as outlined below:

  • Class A fires include those that involve ordinary combustible materials such as wood, cloth, paper, rubber, and many plastics.
  • Class B fires include those that involve flammable liquids, oils, petroleum greases, tars, oil-based paints, solvents, lacquers, alcohols, and flammable gasses.
  • Class C fires include those that involve energized electrical equipment where the electrical nonconductivity of the fire extinguishing agent as discharged is of importance.
  • Class D fires include those that involve combustible metals such as magnesium, titanium, zirconium, sodium, lithium, and potassium.
  • Class K fires include those that involve cooking appliances with flammable cooking oils and fats.

How you can help

Our Standards are developed through a consensus-based process, which integrates scientific and testing expertise with input from our Standards Technical Panel (STP) members and stakeholders. STP members represent a variety of interests, including industry, academia, government, retail and manufacturing. If you are involved in the design, construction, sale and operation of fire extinguishers, and you would like to help improve safety in your industry, please submit a proposal or apply to join STP 711.