What Triggers Fire Sprinklers – And Can They Activate Accidentally?
What Triggers Fire Sprinklers?
Fire sprinklers are activated by heat, not smoke. Each sprinkler head contains a small sealed frangible glass bulb filled with a special heat sensitive liquid. When the surrounding air reaches a specific temperature, this liquid expands, causing the glass to break and releasing water to suppress the fire.
Typical activation temperatures:
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Residential Sprinklers: Trigger at approximately 56°C.
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Commercial & Warehouse Sprinklers: Typically activate at 63°C or higher, as these environments tend to get warmer and require a higher trigger point to avoid false activations.
It is very unlikely that sprinklers will go off accidentally.
Fire sprinklers are a vital part of modern fire protection systems, but many people don’t fully understand how they work or worry they might go off accidentally. Here’s a clearer more detailed breakdown of what actually triggers a fire sprinkler and how likely it is to activate without a fire.
How Do Fire Sprinklers Work?
Once the heat threshold is reached, the glass bulb breaks and water is immediately released from that specific sprinkler head. The water helps cool the area, suppress the flames, reduces vital oxygen reaching the fire thus dampening down the flames and stopping the fire from spreading.
How Long Do Sprinklers Run For?
Domestic systems (mains-fed): Continue running until manually turned off using an isolator valve
Domestic systems (pump & tank): Typically run for 10 minutes
Residential buildings (e.g., care homes, flats, B&Bs): Usually designed to operate for 30 minutes
In properties with concrete floors or extended evacuation needs, systems may run for up to 60 minutes
Can Sprinklers Be Set Off Accidentally?
It’s highly unlikely. Fire sprinklers won’t activate from:
- Casual contact or being bumped
- Smoke, dust, steam, or vapour
- Cooking fumes or vaping
The only things that will set them off is:
Direct and sustained heat at the activation threshold.
Physical damage to the sprinkler head (e.g., deliberate vandalism)
In high-risk settings like schools or mental health facilities, tamper-resistant systems, such as dry-pipe sprinklers without the fragile glass bulbs, can be installed for added safety.
Do all sprinkler heads go off at once?
No. Only the sprinkler closest to the fire will activate. This targeted response limits water damage.
Can incense, candles, or laser pointers trigger them?
Not under normal use. You’d have to hold a flame or heat source under the sprinkler for an extended period to cause activation. Laser pointers don’t produce nearly enough heat to be a risk.
What’s in the glass bulb?
A coloured organic liquid that expands with heat. When it reaches the designated temperature, it breaks the bulb and activates the sprinkler.
Do fire sprinklers detect smoke or vapour?
No. Sprinklers respond only to heat – not smoke, steam, or vapour from vaping.
Summary: Are Fire Sprinklers Reliable?
Yes – fire sprinklers are precisely engineered to activate only when truly needed. With no reliance on electricity or batteries, they’re a dependable line of defence in any fire safety system. Properly installed and maintained, they’re extremely unlikely to activate accidentally.
If you’re considering installing a fire sprinkler system or upgrading an existing one, it’s always best to consult a certified fire protection specialist to ensure the system is tailored to your building’s needs and complies with the latest UK safety standards.
For more information on how fire sprinklers work, check out our Fire Sprinkler Activation Guide and these additional resources:
If you would like more information on how fire sprinkler heads work and what activates or if you need to order or discuss a project get in touch with the team.
