Multi-Sensor Detectors: Benefits and Day/Night Modes

Multi-sensor detectors combine more than one sensing element — typically smoke and heat — in a single device. They can be programmed to behave differently at different times of day, which helps reduce false alarms while still giving good protection.

What is a multi-sensor detector?

A multi-sensor (or multi-criteria) detector uses two or more technologies together. The most common combination is optical smoke and heat. Some also include carbon monoxide sensing.

Because the detector looks at more than one signal, it can distinguish real fires from cooking, steam or dust more effectively than a single-sensor device.

Day/night and change-of-use modes

Many addressable systems allow detectors to switch mode automatically by time of day or by a manual change of use.

• Day mode — often heat-only or a less sensitive smoke setting, useful in kitchens, workshops or areas with temporary smoke or dust
• Night mode — full smoke and heat sensitivity when the building is unoccupied or sleeping
• Change of use — for example a school hall used for events, or a hotel kitchen that is only active at certain times

This is set up in the cause-and-effect programming so the system matches how the building is actually used.

Where this helps

• Hotels — guest rooms at full sensitivity overnight; service areas adjusted during the day
• Schools — kitchens and workshops in day mode; full coverage when the building is empty
• Commercial kitchens — reduced false alarms from cooking while still protecting the space
• Warehouses — different settings for occupied and unoccupied periods

Benefits

• Fewer false alarms from cooking, steam or dust
• Better protection when the building is unoccupied
• One device can cover different uses without extra detectors
• Supports compliance with BS 5839 when programmed correctly

What to consider

Day/night modes must be designed as part of the fire strategy. The responsible person needs to understand when modes change and ensure weekly tests still cover the system correctly. Modes should be documented in the cause-and-effect matrix and reviewed if the building use changes.

If you are planning a new system or reviewing false alarms on an existing one, we can advise on multi-sensor detectors and suitable day/night programming. Contact us for a survey.

Fire detection systems · Fire alarm installation