Glossary — Detection & Alarms
Heat Detector
A heat detector triggers when temperature exceeds a set threshold or rises unusually quickly — without being activated by smoke, steam, or dust. It is the correct detector type for kitchens, garages, and other locations where smoke alarms would produce constant false alarms.
Definition
Heat detector — a fire detection device that responds to an increase in ambient temperature. Fixed temperature (FT) models activate when temperature exceeds a set point (commonly 57 °C). Rate-of-rise (ROR) models activate when temperature increases faster than a defined rate (typically 8–10 °C per minute). Most modern units combine both principles.
Heat detector types compared
| Type | Activates when… | Best use |
|---|---|---|
| Fixed Temperature (FT) | When air temperature reaches a set point — typically 57 °C or 83 °C | Kitchens, boiler rooms, garages |
| Rate of Rise (ROR) | When temperature rises faster than ~8–10 °C per minute, regardless of absolute temperature | Attic spaces, plant rooms, storage areas |
| Combined FT + ROR | Either condition — whichever occurs first | Garages, kitchens, utility rooms, basements |
Why heat detectors matter in kitchens
The kitchen is the highest-fire-risk room in most homes but also the worst environment for a smoke alarm — the normal aerosols from grilling, toasting, and frying trigger false alarms constantly. Many householders disable kitchen smoke alarms as a result, leaving the room entirely unprotected. A heat detector solves this: it cannot be triggered by cooking fumes, yet will activate if a pan fire or oven fire produces the heat of a real fire.
The trade-off is speed. A heat alarm responds later in the fire's development than a smoke alarm. In a kitchen with a clear link to the rest of the house (open-plan living), fitting a heat detector in the kitchen zone and a smoke alarm in the hallway/living area gives the best balance of early warning without false alarms.
BS 5839-6: the domestic detection standard
BS 5839-6 is the British Standard for fire detection and alarm systems in domestic premises. It classifies systems by grade (power supply and interlinks) and category (coverage level). For most owner-occupied homes, a Grade D (mains-powered, battery backup) Category LD2 system — covering escape routes and high-risk rooms — is the recommended minimum. This includes optical smoke alarms in hallways and landings plus a heat alarm in the kitchen.
In Scotland, the Housing (Scotland) Act 2014 (Tolerable Standard requirements effective February 2022) mandates interlinked alarms including a heat alarm in every kitchen.
Heat detectors vs smoke detectors: detection speed
In a typical flaming fire, a smoke alarm will activate 2–4 minutes earlier than a heat detector. In a slow smouldering fire (e.g., a cigarette in upholstery), a smoke alarm may activate 30+ minutes before the heat detector triggers. This is why smoke alarms are the primary detection device in most of the home. Heat detectors fill the specific gap where smoke alarms are impractical.
For full guidance on smoke alarm selection and placement, see our smoke alarm placement guide and the smoke detector types glossary entry.
Frequently asked questions
FAQ