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Frequently asked questions regarding fire sprinklers

We recommend fitting automatic sprinkler systems where appropriate.

More information about the use of sprinklers can be found at:

Questions and myths about sprinkler systems

Are automatic sprinklers a recent invention?

No. The oldest recorded use of automatic sprinklers was in the Theatre Royal, Drury Lane in 1812. The updated version is still in use today.

Are they likely to go off by mistake?

No. The likelihood of a sprinkler turning on accidentally is 1 in 500,000 (per year of service) about the same as being struck by lightning.

Do all the sprinkler heads operate at once?

No. Each head is a self-contained heat detector and is designed to operate when the set temperature is reached. Normally sprinklers are set to operate at 68°C, and only the head that is near a fire will operate. This is why they will not false alarm, unlike smoke detectors that may operate if you burn toast.

Do sprinklers create more water damage than the fire service?

No. Depending on the type of system and the type of premises it is designed to protect, each sprinkler head discharges between 50 -100 litres of water per minute. Typically the discharge begins about 10 -30 seconds after the fire produces enough heat to operate the sprinkler. This is in contrast to the 1,000 - 2,000 litres per minute of water that is likely to be used by the fire service, due to the time taken to respond to the incident. Even if you have automatic fire detection, the time taken for the fire service to respond will be greater than the time taken for the sprinkler to work.

If a sprinkler false alarms, won't it create a lot of damage?

Sprinkler systems cannot false alarm as they only operate if the air surrounding the head reaches a set temperature. They do not respond to smoke, steam, dust or sprays from aerosols.

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How does a sprinkler work?

A sprinkler head is a temperature-controlled valve that releases a spray of water when the heat sensitive element reaches a set temperature. Most sprinklers installed in the UK are of the 'glass bulb type'. This bulb is filled with a coloured liquid and a small bubble of vapour.

As the bulb heats to its operating temperature the vapour expands, until the glass bulb is broken allowing water to escape from a pipe.

The sprinkler head is designed to operate at 30°C above the highest anticipated ambient temperature. Under normal conditions, in temperate climates, a rating of 68°C or 74°C will be suitable. However, sprinkler heads with a operating range from 57°C to 230°C are available as needed.

Is there a risk of vandalism to the system?

Regardless of the type of fire protection system used there is always the chance of vandalism. However, this is extremely rare and the vandal would get very wet and be easy to identify. All sprinkler systems should be fitted with water flow alarms that alert when a head operates. This alarm can be connected to an alarm receiving centre that will alert the fire service.

Deliberate damage to any part of a sprinkler system is a criminal offence.

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Is there a risk of Legionnaire's disease from sprinklers?

Research carried out by the Fire Protection Association and the Loss Prevention Council has shown that there is no realistic chance of a member of the public contacting Legionella pestis from a sprinkler system when it operates.

There may be a small risk to engineering and maintenance staff; this can be entirely eliminated by proper maintenance of the system. There has been no recorded case of Legionnaire's Disease being contracted from any fire protection system anywhere in the world.

Are sprinklers expensive to maintain?

Unlike other fire protection systems that rely on electronics sprinkler systems need only very basic maintenance. Usually only two maintenance visits per year are needed to keep the system in good working order. Weekly and monthly checks of pumps, pressure gauges and valve settings can be carried by trained staff.

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