Smoke or Heat Detector? Choosing the Right Sensor for Every Room

01Smoke detectors: the early warning

Optical (photoelectric) smoke detectors shine a light inside a small chamber. When smoke enters, it scatters the light onto a sensor and the detector goes into alarm. They react well to slow, smouldering fires, the kind that start in wiring, furniture or bedding, often long before there are any flames.

Use them in bedrooms, corridors, offices, stores, server rooms and along escape routes.

02Heat detectors: for rooms where smoke is normal

Heat detectors ignore smoke and steam and respond to temperature instead. Fixed-temperature types trigger at a set point; rate-of-rise types trigger when the temperature climbs unusually fast.

They are the right choice for kitchens, pantries, generator rooms, boiler rooms, car parks and dusty workshops, where a smoke detector would cause false alarms.

03Multi-sensor detectors

Multi-sensor detectors combine an optical smoke sensor with a heat sensor and weigh both readings before raising the alarm. That makes them less prone to false alarms while staying sensitive, which is why they are popular in hotels, hospitals and offices.

04A quick room-by-room guide

• Bedrooms, corridors and offices: optical smoke
• Kitchens and pantries: heat
• Car parks, generator and boiler rooms: heat
• Server and electrical rooms: optical smoke
• Hotel rooms and hospital wards: multi-sensor
• Bathrooms and shower areas: no detector, as steam causes false alarms

05Spacing and placement

Each detector covers a limited area. As a common reference, BS 5839-1 says no point under a flat ceiling should be more than 7.5 m from a smoke detector, or 5.3 m from a heat detector. Installations in India follow IS 2189, and your designer will adjust spacing for ceiling height, beams and airflow.