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4 Hollywood Sprinkler Myths Busted

November 15, 2013

My boyfriend has worked around trains for most of his career. Whenever he sees a new action movie with someone running alongside a train or a commercial showing the engineer driving the train from the wrong side (here’s lookin’ at you, Washington State Lottery!) he gets annoyed. I used to laugh at him, until one night we were watching a movie and a fire occurred in an office and the sprinkler system went off. I mean all of the sprinkler heads went off. And the entire office was flooded. That’s just not reality! So I thought I’d investigate and debunk some Hollywood myths about automatic fire sprinkler systems:


Myth #1: Smoke will trigger a sprinkler system to go off.

Reality: In an effort to escape, a bad guy lights a cigarette. He starts on his glorious speech as the smoke wafts toward the ceiling. As he finishes his talk, with everyone sitting in rapt attention, the sprinkler system goes off, the building is flooded, and the bad guy escapes. Nope. Sorry. Automatic fire sprinklers work using either a fusible link or frangible bulb. This bulb or link (depending on the sprinkler head installed) activates due to a change in temperature, not by smoke particulate. In a frangible bulb, liquid is kept inside of a glass tube. When the heat reaches a certain temperature (165 degrees Fahrenheit in most office buildings, but it can be more or less depending on the application), the liquid expands causing the glass to shatter. Once the glass shatters a flange is released and the water comes out of the sprinkler head. How these heads operate varies by system, but it’s essentially always the same…. This brings us to Myth #2.


Myth #2: When one sprinkler head goes off, all sprinkler heads go off.

Reality: This occurs in one very famous Hollywood movie. Our action hero needs to distract the bad guys, so he sets off the system with his lighter and the building is flooded, giving him his chance to save the day. But this really wouldn’t happen unless you have a deluge system.  Deluge systems are used only in very specific applications and are not that common. In the majority of sprinkler systems, only one head is activated at a time. As heat spreads, more sprinkler heads are activated. In a deluge system, once one head is activated, they will all go off. Studies have shown that in a majority of fires, fewer than eight sprinkler heads are needed to control the blaze.


Myth #3: Sprinkler systems can be set off using a cigarette lighter.

Reality: This is a common scene in movies. The bad guy, or good guy, in an effort to distract everyone, uses his cigarette lighter up close to the sprinkler head, activates it, and floods the building. Refer to Myth #2, as they’re closely related. While the flame from a cigarette lighter, if held closely enough, could activate a sprinkler head, it would only ever do just that. Activate one sprinkler head. The water would immediately put the small flame out and you’d get a pretty good shower. It wouldn’t flood your building as only one head would go off from this amount of heat (unless, of course, it’s a deluge system).


Myth #4: Sprinkler systems can be set off by pulling a switch or fire alarm.

Reality: Once again, looking to escape a bad situation, our hero pulls the fire alarm and activates the sprinkler system, confusing the enemies and allowing his escape. Sorry, but another no. As we’ve discussed, automatic sprinkler system heads are activated by heat from a fire. While they are linked to the fire alarm, they cannot be activated by pulling a simple handle (although there are deluge systems that can be activated this way). The system can be entirely shut down by tampering with either the gate valve or butterfly valve (depending on the type of sprinkler system installed).


fire sprinkler valves

The above picture shows two indicating gate valves.
If they are closed, water cannot enter the system if the system is tripped


Interested in movies showing improper sprinkler system activation? This article by the Home Fire Sprinkler Initiative lists a few movies that perpetuate these myths.


Article by: Kristen Skinner

5 Comments leave one →
  1. Tyson Lowther permalink
    November 19, 2013 9:06 am

    Good article but completely accurate. There are deluge systems out there that work off by pulling a “handle” and if one head does go, they all go.
    Also, your picture of these valves are not os&y valves that you can use the stem to tell if open or not, they each have a sight window on them that would tell you if open or shut.

    • November 19, 2013 10:39 am

      Good catch! There are deluge systems that operate by pulling a handle. Under Myth #2 we mentioned the exception of deluge systems, but should have been clearer about their exception in this case too.

      You’re right on the OS&Y valves too. That one’s my fault, try not to hold it against the author; apparently I’ve been out of the field a bit too long. 🙂

  2. Anonymous permalink
    October 7, 2014 6:03 am

    Please comment: Do you really need a cigarette lighter to set off the sprinkler head? Couldn’t you break the glass vial with a shoe, or a pencil, or anything, really? I’d like to see a movie where a guy asks for a cigarette lighter, and we expect he’s going to create a flame to set off the sprinkler head, but instead he uses the other end of the lighter to simply break the vial. No flame at all.

    • October 7, 2014 9:22 am

      You’re correct: the vial just needs to be broken, whether by impact or by pressure from the liquid inside heating up. Using a lighter to break the vial would be a really funny way for a movie to address the myth!


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