• How do fire sprinklers work?
• Will smoke set off the sprinkler system?
• Don't sprinklers sometimes go off by themselves?
• When one sprinkler goes off, won't they all go off?
• Why do we have sprinklers in some buildings and not in others?
• Water is flowing from the sprinklers, but the alarms aren't going off. What's going on?

Q:  How do fire sprinklers work?

A:  The water in UCSD's sprinkler system pipes is constantly under pressure. At each sprinkler head, the water is held back by a little plug. When sufficient heat reaches a sprinkler head, depending on the type of mechanism used, one of the following occurs:

• The special solder that holds the sprinkler head together melts
  OR
• The fluid in a glass vial in the sprinkler head expands enough to break the glass

In either case, the plug is released and the water begins to flow. Water will continue flowing until the system is mechanically turned off by an emergency responder.

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Q:  Will smoke set off the sprinkler system?

A:  Absolutely not. It takes actual heat, usually 165 degrees Fahrenheit, to set off a sprinkler.

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Q:  Don't sprinklers sometimes go off by themselves?

A:  Rarely. Fire sprinklers are extremely reliable. The odds against a sprinkler going off without cause are less than 1 in 3.3 million.

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Q:  When one sprinkler goes off, won't they all go off?

A:  Only in the movies! Each sprinkler is independent and must be subjected to direct heat to go off.

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Q:  Why do we have sprinklers in some UCSD buildings and not in others?

A:  The building code requires fire sprinklers only in certain kinds of buildings — hospitals, for example. At UCSD, however, it is general policy to provide sprinklers for all new construction, and try to retrofit sprinklers into existing unsprinkled buildings.

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Q:  Water is flowing from the sprinklers, but the alarms aren't going off. What's going on?

A:  Each sprinkler system is equipped with a waterflow-sensing device connected to the building's fire alarm system. These devices incorporate a variable delay setting to prevent false alarms caused by changes in the campus water system supply pressure. Otherwise, every time the pressure surged, the detector would see a little water moving and activate the alarm. The waterflow-sensing devices at UCSD are set at a 30 – 45 second delay.

If you see a sprinkler operating, and the alarm hasn't yet gone off, it's probably because of this delay feature. However, you should immediately activate the nearest fire alarm or dial 911 to report the situation to the UCSD Police Department.

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If you are a UCSD employee and have a question about fire safety, contact EH&S Fire & Life Safety, (858) 822-5706 or 534-3531.