Automatic fire sprinklers are individually heat-activated, and tied into a network of piping with water under pressure. When the heat of a fire raises the sprinkler temperature to its operating point (usually 165ºF), a solder link will melt or a liquid-filled glass bulb will shatter to open that single sprinkler, releasing water directly over the source of the heat.

 Why are sprinklers so effective?

Sprinklers operate automatically in the area of fire origin, preventing a fire from growing undetected to a dangerous size, while simultaneously sounding an alarm.

Automatic fire sprinklers keep fires small. The majority of fires in sprinklered buildings are handled by one or two sprinklers.

 Who decides design and installation procedures for sprinkler system?

Proper design and installation of sprinkler systems is standardized nationally in a consensus standard promulgated by the National Fire Protection Association - NFPA 13.

A basic premise of proper sprinkler protection is that sprinklers be installed throughout all building areas. Partial sprinkler protection is a game of chance, since a fire originating in an unsprinklered area can overpower sprinklers given a head start.

 Can sprinklers discharge accidentally?

Loss records of Factory Mutual Research indicate that the probability of a standard response spray sprinkler discharging accidentally due to a manufacturing defect is only 1 in 16,000,000 sprinklers per year in service.

 What about water damage?

Reports of water damage due to fires in sprinklered buildings are often exaggerated due to comparisons with the small fire loss which occurs thanks to the sprinklers.

The amount of water which is put on a fire by fire department hoses in an unsprinklered building fire is nearly always tens to hundreds of times more than that which sprinklers would have discharged. During a fire, only those sprinklers closest to the fire activate, limiting the total amount of water needed. The fire damage, as reflected by insurance claims, is also many times greater.

    source: nfsa.org