How Does A Fire Sprinkler System Work?
A fire sprinkler system is a critical component in a property’s fire safety, designed to detect and suppress fires automatically and efficiently. Understanding how these systems work is key for building developers and property owners alike, due to their value in protecting property and saving lives.
In fact, the installation of fire sprinklers has the potential to reduce injuries by at least 80% and cut property damage by 90%, minimising environmental harm.
Below, we explore how fire sprinklers work and how they activate, and cover some of the myths surrounding them.
What triggers fire sprinklers?
How a fire sprinkler system will be activated depends on the type of sprinkler installed. The two common types of sprinkler head release mechanisms are glass bulbs and fusible links.
A glass bulb fire sprinkler consists of a bulb filled with heat-sensitive liquid. In the event of a fire, this type of sprinkler will activate when the temperature increases, causing the liquid in the bulb to expand. At a temperature of around 68c, the liquid in the bulb will expand, shattering the glass and releasing a valve to allow the flow of pressurised water through the sprinkler head and onto the fire.
Fusible link sprinkler heads operate similarly. However, the pressurised water is released when a fusible link made from low-melting allow melts.
Each sprinkler head will operate independently in the event of a fire, meaning that water will only be released in order to prevent the fire from spreading, minimising the water damage to the property.
How long do fire sprinklers stay on?
A sprinkler will only remain active and release water until the fire has been extinguished, or until the water supply is manually shut off.
The duration of how long the fire sprinklers stay on for will depend on the occupancy type and the sprinkler’s design. Common run times will vary between 30 and 90 minutes.
The system’s design will depend on the fire risk of the building;
- Light hazard (LH): 30 minutes
- Ordinary hazard (OH): 60 minutes
- High hazard (HH): 90 minutes or longer
The BS9251 fire sprinkler safety standard also gives guidance on how long fire sprinkles should run for. This will depend on the type of building, divided into four risk categories, each with specific requirements.
Category 1 applies to individual dwellings such as houses, flats and maisonettes, HMOs and B&Bs and boarding houses. These must have a minimum run time of 10 minutes, with 1 or 2 sprinkler heads for calculation, a flow rate of 84-100 litres per minute and a tank size on 1m3 to 1.5m3.
Category 2 applies to blocks of flats under 18m, small residential care homes and sheltered and extra care housing. These must have a minimum run time of 10 minutes, with 1 or 2 sprinkler heads for calculation, a flow rate of 84-100 litres per minute and a tank size of 3m3 to 4.5m3.
Category 3 applies to large residential care homes, student accommodation, dormitories and hostels. These must have a minimum run time of 30 minutes, with 2 or 4 sprinkler heads for calculation, a flow rate of 168-200 litres per minute and a tank size of 6m3 to 9m3.
Category 4 applies to blocks of flats 18m or higher, typically 6 floors or more. These must have a minimum run time of 60 minutes, with 2 or 4 sprinkler heads for calculation, multiple tanks, each capable of providing at least 50% of the required water supply, and a backup power supply.
How sensitive are fire sprinklers?
The sensitivity of a sprinkler head will depend on their location. When installed in common residential and office settings, residential fire sprinklers and commercial fire sprinklers will activate at temperatures above 68c. In settings where the temperature will likely be higher, for example in an industrial setting or where there is heat-producing equipment, sprinklers will likely have a higher operating temperature of between 79c and 141c, or even higher in specific requirements.
Specific temperature ratings allow us to minimise false activations from non-fire related situations, such as heat from cooking in residential occupancies.
Will fire sprinklers detect smoke?
No, fire sprinklers will not detect smoke. They are only designed to respond to heat in the event of a fire.
Commonly, buildings will use a sprinkler system alongside smoke detection systems to increase the level of fire safety.
In an emergency, fire alarms and smoke detectors will raise an alarm to allow occupants to evacuate safely, whereas fire sprinklers will control and prevent the fire from spreading.
Will fire sprinklers go off accidentally?
Sprinkler systems are designed specifically to not go off accidentally. A false alarm is an incredibly rare occurrence.
Fire sprinklers are precisely calibrated to require sustained heat in order to activate. Therefore, holding a candle directly underneath a fire sprinkler may trigger it after an extended period, however normal use of candles, incense or similar will not set off a sprinkler accidentally.
Having your fire sprinklers regularly inspected by a competent individual, at least once a year, means that you can have the peace of mind that they will operate in an emergency.
What are the benefits of a sprinkler system?
The benefits of a fire sprinkler system is straightforward. Sprinklers will stop a fire from taking hold and spreading elsewhere within a property, putting out fires quickly and lessening the amount of damage caused.
By slowing the fire’s spread and reducing heat and smoke created, sprinklers will give those within the property more time to evacuate, and lower the risk of firefighter injuries. This can also reduce the risk of a flashover, whilst also safeguarding irreplaceable sentimental items, documents and valuable assets from destruction.
Fire sprinkler care and maintenance
When your property has fire sprinklers, there are a few things to keep in mind. Never turn off the sprinkler stop valve and be careful when the property is being decorated. When painting the ceiling, never paint over the circular plates where the sprinkler heads sit. This could inhibit the sprinkler heads from dropping in the event of a fire.
It’s also important to book an annual service with a qualified engineer to ensure that your whole system is in full working order. An engineer will be able to test the water supply, check for leaks and make sure that the sprinkler system works as designed and hasn’t been modified or obstructed in any way. They’ll also be able to check all alarms.
Meeting fire sprinkler regulations
In the UK, fire sprinkler systems are covered by a robust framework of standards and building regulations to ensure high levels of safety within a property. Understanding these regulations is a fundamental part of responsible building. These British Standards provide comprehensive guidelines of the design, installation, maintenance and testing of these systems to ensure that they perform as intended.
Recently, legislative changes have come into place, in the wake of the Grenfell Tower fire, strengthening the requirements for particular building types.
This is why partnering with a certified and experienced fire protection company ensures that your project adheres to all relevant British Standards and regulations, future-proofing your property and demonstrating your commitment to safety.
Here at Hydro Protect, we design, install and maintain fire sprinkler systems, ensuring that they meet all standards set out by UK legislation. All of our sprinklers meet the highest standards. Get in touch with our team for a full no-obligation quote on your new sprinkler system.