How to choose the right type of fire detector

Direct answer

The right fire detector for a location depends on the fire risk, the environment, and how quickly detection is needed — not on a single "best" device. As general guidance, optical (photoelectric) detectors respond well to smouldering, smoky fires; heat detectors suit areas where smoke or fumes are normal, such as kitchens, subject to the restrictions BS 5839-1 places on them; for dusty or dirty areas BS 5839-1 gives preference to aspirating smoke detection with mechanical filtration rather than to heat detection; and multi-sensor detectors combine sensing elements to balance early detection against unwanted alarms. BS 5839-1 recommends that the selection and siting of detectors is carried out by a competent designer, informed by the fire risk assessment — not chosen from a general description alone.

Applies to

Products / Models: Hochiki Europe detector ranges (general guidance — confirm the exact model on its data sheet)
Firmware / Version: Not applicable
Region: UK
Standards: BS 5839-1 (selection and siting); BS EN 54-5 (point heat), BS EN 54-7 (point smoke), BS EN 54-10 (flame), BS EN 54-12 (optical beam smoke), BS EN 54-20 (aspirating smoke), BS EN 54-22 / BS EN 54-28 (line heat), BS EN 54-26 (carbon monoxide), BS EN 54-29 / BS EN 54-30 / BS EN 54-31 (multi-sensor)

Why does detector type matter?

Different fires develop differently: some produce visible smoke early, others produce heat first.
The wrong detector type for the environment causes either slow detection or frequent unwanted alarms — see How do I reduce false alarms on a fire alarm system?.
Selection is part of system design, and is recorded in the design documentation along with the system category — see Fire alarm system categories explained (BS 5839-1: M, L and P).

The main detector families (general intent only)

Optical / photoelectric smoke detectors — respond well to the larger smoke particles of smouldering fires. A common general-purpose choice for circulation and living areas.
Ionisation chamber smoke detectors — more sensitive to the small particles of fast, clean-burning flaming fires, and less sensitive to the large particles of optically dense smouldering smoke. Optical is the more common choice in escape routes; ionisation still has a place where the expected fire is fast and flaming.
Heat detectors — respond to a temperature rise or a fixed temperature rather than smoke. They have the greatest immunity to unwanted alarms, so they suit places where smoke or fumes are normal, such as kitchens. They are also the least sensitive type, and BS 5839-1 restricts where they may be used. In particular, BS 5839-1 no longer accepts heat detectors in rooms in which people sleep, in either a Category L2 or a Category L3 system. The recommendation is not retrospective, so an existing system does not have to be changed unless it is being extended or upgraded.
Carbon monoxide fire detectors — respond to the CO produced by incomplete combustion, so they give earlier warning of a smouldering fire than a heat detector with less false-alarm potential than a smoke detector. Their electrochemical sensors have a finite life and need replacing; the user should be told the expected lifetime.
Multi-sensor detectors — combine more than one sensing element (for example optical and heat, and in some models carbon monoxide) and process the signals together to improve early detection while resisting unwanted alarms. Hochiki's ACD-EN multi-criteria sensor, for example, combines optical, heat and CO sensing with selectable response modes (see What does the ACD-EN multi-sensor detect, and how do its CO, smoke and heat functions work?). Check the current data sheet and mode booklet for the exact modes.
Specialised detectors — optical beam, aspirating smoke detection (ASD), flame and line heat detection exist for specific applications and large or difficult spaces; these are design decisions for a competent designer. For dusty or dirty areas, BS 5839-1 gives preference to aspirating smoke detection with mechanical filtration over heat detection.

Where BS 5839-1 restricts each type

Heat detectors should not be used in escape routes of Category L systems; in areas of a Category P system where a small or smouldering fire could cause unacceptable damage; where smoke could threaten escape before people or heat detection would notice it; or where the heat detectors themselves would cause a high rate of unwanted alarms. BS 5839-1 adds rooms in which people sleep.
Smoke detectors should not be used where the main fire hazard is flammable liquids or gases that produce little smoke, or where they would cause a high rate of unwanted alarms and another type would respond fast enough.
In Category L systems, smoke detectors in corridors and stairways forming escape routes should be of the optical type, unless optical detectors would significantly increase the rate of false alarms.
Take the exact wording and any further exclusions from the current BS 5839-1; the list above is a summary, not the standard.

How the choice is actually made

The detector type, location and spacing are determined by the fire risk assessment and a competent designer, taking account of the room use, ceiling height, ventilation and likely fire type.
BS 5839-1 gives recommendations on detector selection and siting; the design records which type is used where.
Do not change a detector to a different type (for example swapping a smoke detector for a heat detector to stop unwanted alarms) without a competent person confirming it still meets the system design and BS 5839-1.

When to contact technical support

If you need to confirm which Hochiki detector models suit a particular environment or are compatible with your system.
If you are experiencing false alarms and are considering whether the detector type is appropriate — investigate the cause with a competent person rather than changing devices in isolation.

Safety note

This article is general guidance for Hochiki Europe products. Design, installation, commissioning, maintenance and modification of fire detection and alarm systems should be carried out by, or under the responsibility of, a competent person in accordance with the applicable standards (for example BS 5839-1 in the UK). Statutory requirements imposed by the relevant enforcing authority also apply. Always refer to the current product manual and data sheet for the exact model before carrying out any work.

References

BS 5839-1 (current edition) — detector selection and siting recommendations
BS EN 54-5, BS EN 54-7, BS EN 54-10, BS EN 54-12, BS EN 54-20, BS EN 54-22 / BS EN 54-28, BS EN 54-26, BS EN 54-29 / BS EN 54-30 / BS EN 54-31 — detector type definitions
Product data sheets for the specific detector models

Last reviewed: 2026-10-21 — Reviewed by: Hochiki Europe Technical Support