Flammable antifreeze in fire sprinklers allegedly causes explosion

In August of 2009 in Truckee, CA, a man was cooking on a stove when the pan caught fire, activating the fire sprinklers. Upon activation of the sprinklers, a violent explosion occurred which resulted in 1 death and 4 burn injuries to the family.

I came across this copy of a report (from the IAFSS mailing list) which details a report of a cooking fire turned explosive when the sprinklers were activated. Allegedly the propylene glycol used in the fire sprinkler system as an antifreeze aided in the explosive event, and another case is cited in which the antifreeze ignited and assisted in growing the fire from its ignition source.

The report can be found here: California –explosion– report (PDF)

While I have taken a few courses in fire sprinkler systems, I am not extremely familiar with the flammability of antifreeze such as propylene glycol, but allegedly the atomization of the droplets causing the liquid to become flammable was the cause of this explosion. More flammability and MSDS hazard info is cited in the report.

The report presents many questions at the end which would be useful in quantifying the relationship of the antifreeze in this case, especially since (to my understanding) propylene glycol is the most widely used antifreeze in sprinkler systems. I look forward to finding out more about this topic, and I think it’d be a great research project for a student or research firm to take on.

Posted in fire, News, Science
5 comments on “Flammable antifreeze in fire sprinklers allegedly causes explosion
  1. Kris Overholt says:

    Update to this post:

    Some other FPEs have commented on this story, saying that there is no way that the antifreeze was flammable even in a 50/50 mixture, and doubtful for a 100% mixture (which is unlikely). Even an atomized mixture of water and propylene glycol would apparently not be flammable. More likely was that the high velocity of water and antifreeze mixture would agitate a grease fire enough to appear “explosive”.

    As you noticed when I posted this, I used “allegedly” and “might have” a lot as I was skeptical that a commonly used antifreeze solution would be flammable in any situation. This kind of stuff is tested in many anecdotal experiments and setups by the listing companies and manufacturers. In conclusion, I disagree that the antifreeze became flammable under these circumstances and although the fire I posted was fatal due to the initial fireball caused by the sprinkler, the sprinklers did activate and wet other fuels around and keep the fire from spreading further.

  2. Kris Overholt says:

    Update from NFPA:

    NFPA issues safety alert regarding antifreeze in residential sprinklers:

  3. Tanya Soffen says:

    Hey Kris

    I heard about this fire a few days ago actually when it came up during a meeting at work. I stumbled across this whilst googling the fire and am really excited to read this other paper. I just read the NFPA stuff that they just recently published. It’s interesting to think after taking FPE classes and learning so much that something like antifreeze would cause an explosion.

    It’s my understanding that the NFPA 13,13D and 13R standards state in the code that the antifreeze should be premixed before entering the system and should only be a certain antifreeze to water ratio. From what I hear it was a 79% antifreeze to 21% water in the system (this is just hear say I can’t say it’s true)

    Not sure if you read this or not but here’s a paper NFPA did… some verification of antifreeze solution was done through UL testing as well


    I think it’s veyr dependent on the sprinklers used and discharge rates from the system.

    Just my two cents. Hope all is well.

  4. I feel that the recommendations are a little strong as they have not been able to replicate the spray fire conditions where the concentration is 50% or under. I appreciate that the concentration could vary if not mixed properly causing a higher concentration in drops but still feel that the reaction is a little over the top.

  5. An update to this Kris –

    Results of the Scope A testing indicated that concentrations of propylene glycol exceeding 40% by volume and concentrations of glycerin exceeding 50% by volume have the potential to ignite when discharged through automatic sprinklers. The potential for ignition depends on several factors including the ignition source, sprinkler model, sprinkler elevation, discharge pressure, and the location of the sprinkler with respect to the ignition source. Ignition of antifreeze spray increased the measured heat release rate in certain tests with 50% propylene glycol and 55% glycerin by more than 300%. For certain test conditions, the increase in heat release rate
    resulting from the application of 55% glycerin solution exceeded the increase in heat release rate from the application of 50% glycerin solution by a factor of 10. A similar level of sensitivity was observed between 40% and 50% propylene glycol solutions, but not between 40% and 45% propylene glycol solutions.

    The results of the Scope B testing indicated that concentrations of propylene glycol not exceeding 40% by volume and concentrations of glycerin not exceeding 50% by volume have
    similar performance to water as compared to the UL 1626 fire control criteria. Tests with the 40% propylene glycol and 50% glycerin solution met the UL 1626 fire control criteria and
    demonstrated similar performance to water throughout many of the tests.

    The results of this research suggest that antifreeze solutions of propylene glycol exceeding 40% and glycerin exceeding 50% by volume are not appropriate for use in home fire sprinkler systems. Consideration should be given to an appropriate safety factor for concentrations of antifreeze solutions that are permitted by future editions of NFPA 13, as well as warnings and
    limitations outlined in antifreeze product literature. In addition, based on the flammability properties outlined in Table 4, the use of solutions of diethylene glycol and ethylene glycol in
    home fire sprinkler systems should also be limited.

    Very interesting results

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