Optical Smoke Alarms

An optical smoke alarm shines a light inside a dark chamber, and smoke entering the chamber scatters that light onto a sensor, which sets off the alarm. It responds well to slow, smouldering fires and typically gives fewer false alarms from cooking than ionisation types. The range here includes battery, mains and addressable optical alarms and detectors.

Yes. Photoelectric is another name for optical smoke detection, where the alarm senses smoke by the light it scatters inside a dark chamber. When comparing alarms, check the power source, interlink options and approvals rather than the name. The range here includes photoelectric optical detectors.

In UK homes, optical alarms are usually recommended for hallways, landings and living rooms, as they respond well to smouldering fires. Ionisation alarms typically react quickly to flaming fires but are more prone to nuisance alarms from cooking, and they are now less common. Kitchens usually need a heat alarm instead. The range here includes optical and multi-sensor alarms.

A short chirp at regular intervals usually means a low battery, a fault, or that the alarm has reached the end of its life. Check the indicator light against the maker's instructions, replace the battery where it is replaceable, and clean dust from the vents. Alarms with a sealed battery are usually replaced as a unit. The range here includes replacement optical alarms.

No. An optical smoke alarm senses smoke particles, not carbon monoxide, which is an invisible gas with no smell. Rooms with a fuel-burning appliance, such as a gas boiler or wood burner, need a separate carbon monoxide alarm. Some combined alarms sense smoke and carbon monoxide in one unit, so check what the alarm senses before buying.