• Extinguishers: Understanding Travel Distance for Class B Spill Fires

    By Mark Conroy

    Our industry uses the term “travel distance” as a measurement from a starting point to an extinguisher. Although the code requirements are based on a measurement in one direction (from the hazard to the nearest extinguisher), the effect relates to the time it takes for a person to travel from a fire in order to retrieve an extinguisher and then return to the fire to begin extinguishment. An understanding of travel distance, as it relates to Class B spill fires, will help you determine the most appropriate placement of extinguishers for this type of hazard.

    Maximum Travel Distance

    Flammable liquid fires reach their maximum intensity almost immediately. That is the reason the maximum travel distance is 50 ft for Class B extinguishers vs. 75 ft for extinguishers intended for slower developing Class A fires. Also Class A protection is required throughout buildings, so travel distance for Class A is measured from any point to the nearest extinguisher. But Class B hazards are not normally everywhere in a room, unless the building is an automotive repair garage or something similar. That is why the travel distance is measured from the potential spill area to an extinguisher. Another consideration is that travel distance is the actual walking distance, which is affected by partitions, walls, doorways, aisles, and similar walking restrictions. A person needs to walk around these obstructions.

    Two Travel Distances

    Although the maximum travel distance is 50 ft, a shorter 30 ft travel distance is permitted. The 30 ft allowance relates to quicker retrieval and faster application of extinguishing agent on a fire, allowing for a smaller extinguisher. Over time, the heat of the fire increases, so it makes sense that a larger extinguisher is needed for 50 ft travel distance, while a smaller extinguisher is allowed for 30 ft travel distance. Many fire protection decisions are based on economics, so the 30 ft travel distance rule is applied wherever practical (smaller extinguishers often mean less cost to customers).

    Extinguisher Rating Based on Flammable Liquid Quantity and Travel Distance

    Light < 1 Gallon 5-B 10-B
    Ordinary 1-5 Gallons 10-B 20-B
    Extra > 5 Gallons 40-B 80-B

    One Extinguisher for Multiple Hazards

    Only one extinguisher is installed wherever it can be used to protect more than one hazard area. For example, one smaller extinguisher (30 ft rule) can be installed between two hazards that are 60 ft (or less) apart. Another example is where the hazards are over 60 ft but no more than 100 ft apart. One larger extinguisher (complying with the 50 ft travel distance rule) is needed for this example. For both examples, the extinguisher is installed so that the maximum travel distance from each hazard is not exceeded. With an understanding of the basic concepts for travel distance, as it applies to Class B fire hazards, you can provide the most practical solutions for the protection of your customers’ facilities. Additionally, you will gain their respect while feeling confident that you are doing your job correctly and in compliance with NFPA 10, Standard for Portable Fire Extinguishers.

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    Mark Conroy is an engineer and code consultant at BHC Inc. and a member of the NFPA Technical Committee on Portable Fire Extinguishers.

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    Disclaimer: The opinions expressed in the above Tech Series article are the author’s only and provide limited information. Although the information is believed to be reliable, Brooks Equipment Company, LLC expressly disclaims any warranty with respect to the information and any liability for errors or omissions. The user of this article or the product(s) is responsible for verifying the information’s accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.