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November 5, 2012 5:44 AM   Subscribe

How did "fire alarm goes off" → "sprinkler gets activated" become a TV trope? Have there ever been systems in wide use that act like this?
posted by dmd to Society & Culture (11 answers total) 1 user marked this as a favorite
 
I don't think there needs to be a system that works like that; it's just how everyone thinks they work.
posted by Admiral Haddock at 5:51 AM on November 5, 2012


Yes, that's my question. Why?
posted by dmd at 5:53 AM on November 5, 2012 [1 favorite]


Narrative convenience.

Like the tvtropes article says, there ARE flooding systems, but they're more for industrial / large-scale fire hazard areas, where waiting for the entire system to trip will mean a fire gets out of control.
posted by the man of twists and turns at 6:02 AM on November 5, 2012 [1 favorite]


Don't know the history you're asking for, but I can tell you that non-water suppression systems, such as FM-200 (a modern replacement for Halon) often do act in this manner, and those of us who work in environments where they're installed usually (and subconsciously) stay very aware of the location of the exits. They are driven by hardwired alarm sensors and/or manual pulls, and while the sensors can generally be set so that two different sensors have to be tripped before the system dumps its load of suppressant, activating a manual pull will indeed release suppressant throughout the protected zone.

Generally speaking, people should be alarmed about remaining in a room where a fire suppressant agent such as Halon or FM-200 has been discharged, and there are enough deployments of these things that it wouldn't shock me to discover that people confused water-based suppression systems with these systems to some small extent. Whether or not that actually has anything to do with your question is unknown to me, but I thought perhaps it would be interesting to you.
posted by jgreco at 6:03 AM on November 5, 2012 [1 favorite]


This system is still in use over here.

The fire sensor is a small glass capsule that busts when it heats up. It holds a valve closed, when it bursts, the water starts flowing out of that unit.

Down on the side of the building there's a whole mess of pipes and interesting stuff. One of these is a water-propelled motor that opens the main tap. Basically, there's a pressure regulated water source that is connected to all the sensors units. When one opens, the pressure-regulated water sprinkles out of that unit, this flow opens the big, non-regulated tap. The non-pressure-regulated water has enough pressure to break all the other little glass capsules, so water starts flowing out of all the sensor units.

Also connected to the water-propelled motor is an old fashioned mechanical bell. So the moment the water starts flowing, the bell starts ringing.

Couple of places in Cape Town this whole thing is behind glass (I presume so the fire fellows can break the glass and turn the main valve off). Fascinating to study :-)

Here's a bit of a write-up and a picture of the sensor http://3dfire.com/faq.html -- doesn't say much about the system that then breaks all the other bulbs to flood the area, but I'm sure google has it somewhere if you're not bored to death already.
posted by wrm at 6:26 AM on November 5, 2012 [3 favorites]


dmd, I think the why is that few people have been in a situation where the fire suppression system has been triggered, and it's reasonable to assume that triggering one zone of the system 1) sets off an alarm and 2) sets off the other zones in the system. This misconception is reinforced by movies and TV, but it's also a reasonable (if incorrect) guess about how the system works if you've never seen it triggered--I don't think this is based on any any factual existence of systems that work like that.
posted by Admiral Haddock at 6:44 AM on November 5, 2012


It became a TV trope because it carries a grain of truth (i.e. there is a process that bears some resemblance to the one portrayed) and more importantly it drives action as a plot device (i.e. when the water sprays out something nearly always happens afterwards). An imperfect analogy would be the TV trope of the fuel tank exploding - something that is very rare in vehicle accidents but very common on film. In the case of the sprinkler, the what follows next is typically distraction of someone crucial to the plot and/or mass exit of people from the building. To achieve this requires the hero/anti hero to have no specialist equipment and do very little. These are useful plot devices. Like the fuel tank exploding, they work on film because most people have little direct experience of how these things work.

One way to think about these tropes is foreshortening, generalising and simplifying of processes:

- foreshortening - taking a longer process (like fire spreading across a building, or someone hacking an account) and making it shorter
- generalising - taking an action that might apply locally (i.e. a fire triggering an alarm or sprinkler) and applying to a whole system or area.
- simplifying - ignoring inconvenient truths about how stuff really works, or how possible something is.
posted by MuffinMan at 7:16 AM on November 5, 2012 [2 favorites]


I think this is because writers don't think like engineers, so they think about what the sprinkler does, rather than how it works, or how it would work best. Adding drama and chaos means that elements go off in an inconvenient unexpected manner, never mind the work that goes into preventing that from being a normal real-life occurrence.
posted by Sunburnt at 7:56 AM on November 5, 2012


Also the sprinkler going off is a very visual effect and for that reason a very important element in the type of visual storytelling language that writers and directors like to use in TV, film, and video.

Being able to show the connection between the cause and effect visually is much more powerful and direct than simply showing the cause and the effect without being able to show the connection between the two. You could do that, for instance, by showing the alarm go off (visual and audio) and then showing people getting up to leave or whatever. You've got a cause and an effect but the link between the two isn't visible.

But when you can show the flame licking at the sprinkler's sensor, the sprinkler going off and spraying people, the sprayed people jumping up and reacting to the spray in whatever way is appropriate for the plot and scene--now you've go a purely visual story you can tell.

(You'll notice when there is a scene where, say, some kind of flashing light/audible alarm goes off without the sprinkler element, they will generally show both the flashing light itself and the result of the light visibly flashing on the people it is supposed to affect. Or they will use some other technique to visibly connect the alarm and the people/things it's supposed to affect. They will try hard to find some way to visually make the connection and the sprinklers just happen to be a simple, commonly known, and often used way of doing that.)

Someone who has actually studied film or film making could probably fill in a lot more details.

FWIW watching the TV news is a lot more interesting when you watch how they work to visually portray the stories they work on. It also quickly becomes clear how little interest they have in stories that don't have a strong visual element (which is unfortunate, because many very important stories just don't have that element).
posted by flug at 8:37 AM on November 5, 2012


In my college dorm, we were told that if the smoke alarm in our rooms went off, the sprinklers for the entire building would activate, and we would be responsible for the damage if there was no fire and/or we were found to be in violation of the various anti-fire rules.

I'm sure that this was not true at all, but it was a useful method of coercive control (shame and financial responsibility! because you made ramen!)

I also had no idea that this wasn't the case until yesterday. Thanks, MeFi!
posted by charmcityblues at 9:10 AM on November 5, 2012 [1 favorite]


It's true (or WAS true) in every bldg that has those little "asterisk on a stem" thingies sticking out of the ceiling periodically. Their purpose is to produce a mixed-range circular spray of water, and their spacing ensures 100% coverage at the expected water pressure.

Now, what it takes to actually set them off is another question, since a too-easily started sprinkler system is a quick route to financial mayhem in a computer-age business.
posted by IAmBroom at 11:18 AM on November 5, 2012


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