Can you really set off building sprinklers with a Bic lighter?

[Patty O'Furniture]

You see people doing this in the movies in order to create a diversion (see Hollow Man). Good guy climbs up on a filing cabinet, flicks his bic and whooosh the whole place is drenched and our hero escapes as the mayhem ensues.

Is a building's sprinkler system really this easy to set off? If so, then why aren't there more incidents of practical jokers (more like vandals, I guess) wetting down entire department stores & ruining thousands of dollars in clothes? It's usually pretty easy to reach at least one sprinkler head somewhere in the building. In the Hecht Co. department store that's right next door to me, several sprinkler heads are within easy reach as you ooze up the escalator.

On my floor there are sprinkler heads just a couple of feet overhead, ready to release gallons of water onto millions of dollars of public switching equipment. All it would take is one sufficiently disgruntled employee...

[barker]

Automatic fire sprinklers are individually heat activated. Usually set at 165 degrees (F). Each sprinkler head has a solder link that will melt or liquid filled glass bulb that will shatter and release pressure for that individual sprinkler head.

A BIC lighter could set ONE off, but the entire sprinkler system would not set off a flood around you.

[CalMeacham]

This has always bothered me -- it shows up in a LOT of movies (see Aliens for another example), and I think they're taking a lot of dramatic license.

I am not familiar with the sprinkler heads used in suuch offices, or the overall systems, but I have been taught that they use a eutectic piece as a "trigger". A Eutectic is a low-melting alloy (such as Wood's Metal, although I doubt if anyone uses that particular alloy). You can tell which part is the eutectic by looking closely at the sprikler head -- it's the roughly disc-shapoed part of ugly grey metal. The theory is that rising heat or even a flame will melt this part. This releases the cap over the sprinkler, letting the water flow. Eutectics can melt at REALLY low temperatures (Wood's metal melts in hot water), so you ought to be able to melt this using a BIC Lighter.

But here's the thing -- why should melting this ONE disc set off ALL the other sprinklers? THEY still have their discs in place. It also doesn't make sense to soak an entire building or floor because of a fire in one part of it. The system looks as if it should be self-regulating -- the heat only sets off the sprinklers where it's hot enough to need them.

THIS is where I suspect Dramatic License takes over. It just LOOKS so much more impressive to have an entire floor full of sprinklers going off at once. Besides, there's nio practical way you can script it so that you set off all sprinklers at once, shy of setting fire to the whole place.


I might be wrong about the above, but I doubt it. This is the kind of scam Hollywood pulls all the time.

[Running with Scissors]

There are at least two different types of sprinkler systems. The type you're talking about here keeps the system fully pressurized, and each head will turn on as heat hits it. There is another type where the pipes remain empty until a master valve is released (Halon fire supression systems work this way, too). In this type, each head is always open, and opening the valve would cause water to come out of each sprinkler attached to that section of pipe. I would presume that there are electronic sensors scattered about the ceiling that trigger the valve to open; however, it's unlikely that the sensors would be integrated into a sprinkler head.

[KCB615]

As Cal said, most sprinkler heads use a eutectic material in the operating element. This metal melts at 165d F for most standard sprinkler heads. That does not mean that the instant the ambient temperature reaches 165 the head activates. There is a period of heating up, called thermal lag, between the ambient temperature reaching 165 and the head activating. This time varies from model to model.
There are also heads that are activated by a glass bulb instead of a link-and-lever (eutectic metal) design. A glass bulb filled with an alchohol based solution holds the orifice cap in place. When heated, the bulb breaks, releasing the cap, and letting the water flow.
And I agree, there is nothing (well, almost nothing) that irritates me more than seeing someone smoking, pulling a fire alarm pull station, or lighting a match under a sprinkler head on televison/in movies and activating every head in the building.

Picture of glass bulb, pendant style head (http://members.aol.com/KCB615/glass.JPG)
Picture of link-and-lever, eutectic metal pendant style head (http://members.aol.com/KCB615/eut.JPG)


Frog, there are many more types of systems than that. I'll give a rundown of the basic types:

Wet System: The normal, run of the mill sprinkler. The heads are individually activated by heat only, and the pipes are always filled with water.

Dry System: Again, the heads are individually heat activated, but the piping is filled with compressed air. When a head opens, the compressed air bleeds out of the system, which releases the dry pipe valve, allowing water to enter the pipes and thus flow from the open heads. Dry systems are used in areas where there there is a possiblity of freezing (outdoors, inside freezers, etc).

Preaction System: Like the Wet and Dry systems, preactions also have closed heads, but the pipes are filled with air at atmospheric pressure. When a head opens, no water or air comes out. An additional fire alarm system must activate, thus opening a control valve and allowing water to fill the pipes. If a head opens but no alarm sounds, no water flows. If the alarm sounds but no heads open, the pipes fill with water, but no water flows from the head (since its closed). These systems are generally found in computer rooms, where accidental discharge is avoided like the plauge.

Deluge System: This is the "hollywood" sprinkler system. Unlike the wet, dry, and preaction systems, the sprinkler heads on a deluge system are already all open. When a fire is detected by an alarm system (either from pull stations, or heat/smoke/flame detectors), a control valve is opened and water flows from every head. These are normally found in high challenge areas such as aircraft hangars and flamable liquid storage facilities. I've witnessed a test of a deluge system once, let me assure you it is a lot of water.

Thats about it for the water based sprinkler systems. There are also water mist systems, but I'm not going to get into them (they work like deluge systems). Halon, FM200, and dry chemical systems work like a deluge system does, also. Generally heat detectors (and always at least 1 pull station) will sense said fire, thus discharging the agent in one "poof." After the agent tanks are empty, the system shuts off (nothing left to shoot). Sprinkler systems generally discharge until someone shuts them down.


Any questions?