What Sprinklers Do-Environmental Health & Safety - Carnegie Mellon University

Wednesday, April 13, 2011

What Sprinklers Do

sprinnkler head

A sprinkler system is designed to do one thing, automatically extinguish a fire. The system itself is very simple.  Wet sprinkler systems are composed of a series of pipes that hold water.  The piping runs above the ceilings and the sprinkler heads, pictured above, hang down below.  There are some specialized sprinkler heads that are mounted horizontally on walls. There are others that are hidden behind plates, but for the most part, the typical configuration is the pendant head hanging down.

We have all experienced smoke detectors going off and evacuating buildings as a result of a burnt food, steam or dust generation.  Because fires travel so swiftly, smoke detectors are designed to be very sensitive. 

If a single sprinkler is activated, only that head releases water. Sprinklers are not sensitive to normal environmental conditions. The head will only release water when there is a fire below it.  They need temperatures of 135o F or higher to activate. Sprinklers only release water if there is enough heat to physically break the glass tube inside the head.  The only exception is on the rare occasion when the device is accidentally struck. 

What sprinklers don't do.  They do not release water when exposed to smoke or dust.  One head releasing water does not activate every other sprinkler head in the building.  They do not release water if someone pulls a pull station.  This makes good movies and commercials, but is purely theater.

Pittsburgh City's Deputy Fire Chief told me that 90% of all building fires are put out by a single head. 

By: Madelyn Miller, mmiller@andrew.cmu.edu, 412-268-1377