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Frequently Asked Questions
How do sprinkler systems work?
How effective are fire sprinklers?
How do fire sprinklers operate?
How reliable are fire sprinklers?
21 Things you didn't know about Fire Sprinklers
How do Sprinkler Systems work?
Each sprinkler head is held closed independently by heat-sensitive seals.
These seals prevent water flow until a design temperature is
exceeded at the individual sprinkler heads.
Each
sprinkler activates independently when the predetermined heat level
is reached. The design intention is to limit the total number of
sprinklers that operate, thereby providing the maximum water supply
available from the water source to the point of fire origin.
Typical
"wet" systems are simple and passive. They have water
already pressurized in the pipes held back by the sprinkler head.
These systems require no manual controls to activate, so long as
adequate water supplies are provided.
Specialty
systems called "dry" systems, designed for unheated
spaces, have a low "maintenance" air pressure in the
pipes. Water is fed into the system when the sprinkler
"fuses" allowing the maintenance air pressure to reach the
minimum pressure point. "Pre-action" systems are highly
specialized for locations where accidental activation is
unacceptable such as museums with rare art works, manuscripts, or
books. Pre-action valves are connected to fire alarm initiating
devices such as smoke detectors or heat detectors and virtually
eliminate the possibility of accidental water flow.
"Deluge"
systems are "pre-action" systems that have open
sprinklers, i.e. the fusible link is removed, so that every
sprinkler served by the system will discharge water. This ensures a
large and simultaneous application of water over the entire hazard.
These systems are used for special hazards where rapid fire spread
is a concern.
Other
specialty systems may have foam instead of water suppression agents
for fire protection in occupancies with flammable liquids, such as
airport hangars. "Clean agent" gaseous systems, such as
Argon/CO2/Nitrogen mixtures can be used in very small spaces where
water cannot be used for suppression.
A
sprinkler activation will do less damage than a fire department
hose, as the fire department's hose streams provide around 15.0
Litre/Second (200 gallons per minute) whereas an activated sprinkler head
generally discharges around 90 Litres per minute (20 gpm).
How
effective are Fire Sprinklers?
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
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 74ºC/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.
How reliable are Fire Sprinklers?
All fire protection features have a reliability factor. Walls and shafts can be breached by means of poke-throughs and building alterations. Exit doors can be blocked or locked.
Sprinklers may be the most reliable fire protection system known. Detailed fire records for Australia and New Zealand (where fire must be reported) for the years 1886 through 1968 showed that 99.76% of all fires were extinguished or controlled by the sprinklers. Fire records in the US are less dependable due to lack of full reporting, especially for small fires where the sprinklers are successful. Nevertheless, the range includes a 96.2% success record reported by the National Fire Protection Association for the years 1925 through 1969, 98.4% success record for New York City high-rise buildings between 1969 and 1978, and a 98.2% success record for U.S. Department of Energy facilities between 1952 and 1980.