Busting Hollywood Fire Sprinkler Myths | WSRB Blog

Summer is Hollywood blockbuster season and we've decided to update one of our popular posts. Don't worry, we won't spoil any new movies.

How Hollywood thinks fire sprinklers work

Movies often portray automatic fire sprinkler systems as escape routes for heroes or villains, as comic relief, or as a way to change the direction of a scene.  A few examples:

• In "The Incredibles," Mr. Incredible receives a note that self-destructs, emitting a small amount of smoke that sets off the home's fire sprinklers.
• Gavin Banek, the character Ben Affleck portrays in "Changing Lanes," lights a piece of paper on fire and holds it under a fire sprinkler head, triggering not just that sprinkler head but all the others in the office building. 
• Facing a hallway full of out-of-control students, Principal Duvall in "Mean Girls" hits the fire alarm with the end of a baseball bat and sets off all the fire sprinkler heads. Everyone is immediately doused.

Though fun to watch, these depictions of fire sprinkler systems aren't accurate. Let's explore the reality of how automatic fire sprinklers work.

Filmmakers create drama, so their depictions of fire
sprinkler systems aren't always accurate.  

Related:
Home, Sprinklered Home

Myth: Smoke triggers fire sprinklers

In reality, heat sets off fire sprinklers. The sprinkler heads contain heat-sensitive material that doesn't respond to smoke. 

That's good news if you are considering installing fire sprinklers in your home. Burned toast or cooking experiments gone awry won't set off your sprinklers, and neither will self-destructing notes if you happen to receive one.

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

In most automatic fire sprinkler systems, each sprinkler head activates individually. As heat spreads, more sprinkler heads activate, but in about 90% of studied cases, six or fewer heads were sufficient to control a blaze. In more than 80% of cases, two or fewer sprinkler heads controlled the fire.¹

There are deluge systems, but they're used only in very specific applications and are not that common. In a deluge system, once one head is activated, they will all go off. 

High schools, like the one in "Mean Girls," and office buildings, like the one in "Changing Lanes" typically don't have deluge systems, so both Principal Duvall and Gavin Banek would, in reality, need to come up with other plans. 

Myth: You can set off a sprinkler system with a fire alarm or cigarette lighter

Unless the system is a deluge system, pulling a simple handle or hitting an alarm button, as Principal Duvall did, won't activate sprinkler heads. 

If you get close enough, you can set off a sprinkler head with a cigarette lighter. By now, you know you'll only set off that one sprinkler head, though, so you'll want to escape quickly or be prepared to get showered on. 

What about an accurate depiction of fire sprinklers?

In the original "Die Hard," John McClane (Bruce Willis) sees a fire sprinkler head and is inspired to pull the fire alarm in Nakatomi Plaza, the skyscraper where most of the movie takes place. Pulling the alarm sends an alert to the building's security system and to the fire department. That's what McClane wants: to get the authorities to come to the building so they'll see the hostage situation there. Unfortunately, the bad guys are also monitoring the security alerts and foil the plan by calling the fire department to say it's a false alarm.  

Have you seen fire sprinkler myths in movies? Share this post on social media and help us bust some more myths. If you've seen accurate depictions, feel free to share those, too. Just one request: let's keep summer blockbusters fun for all and not spoil any new movies.  

[1] Tufts University, https://publicsafety.tufts.edu/firesafety/sprinkler-systems/