Mercury Photoelectric Smoke Detector - 10 Year Sealed Battery

The Mercury is a photoelectric smoke detector with a sealed CR123A 3V battery rated for 10 years of continuous operation. The battery is non-removable and factory-installed, eliminating the need for replacement during the detector's working life. A pull-pin on the base activates the internal battery on first installation, and a low-battery warning alert triggers when the unit nears end-of-life after approximately 10 years.

Designed for residential ceiling or wall mounting, the detector uses photoelectric sensing rather than ionisation, making it more responsive to slow-burning fires that produce visible smoke particles before open flame. The 85dB alarm output at 3m provides audible warning across typical domestic room sizes and hallways. The large test/hush button allows weekly testing and can be pressed to reduce sensitivity for 10 minutes when cooking fumes or steam trigger false alarms.

The detector conforms to EN14604:2005 AC/2008 and carries both visual and audible alarm indicators. At 101mm diameter and 34mm depth, it mounts to UK ceiling roses and wall surfaces using the supplied fixings. The white ABS housing suits most domestic interiors and the unit weighs 116g when battery-activated, light enough for plasterboard ceiling installation without additional support.

Product Manual

Can the battery be replaced?

No. The CR123A battery is sealed inside the unit at manufacture and cannot be accessed or replaced. When the low-battery warning activates after approximately 10 years, the entire detector must be replaced.

What's the difference between photoelectric and ionisation detectors?

Photoelectric detectors like the Mercury respond faster to slow-burning, smouldering fires that produce visible smoke before flames appear. Ionisation detectors respond faster to fast-flaming fires with smaller smoke particles. UK fire safety guidance recommends photoelectric detectors for most residential rooms.

How is the hush function used?

Press the large test/hush button on the face of the detector when cooking fumes or steam cause a false alarm. This reduces the unit's sensitivity for 10 minutes, after which normal sensitivity resumes automatically.

Where should smoke detectors be installed?

UK Building Regulations require smoke alarms on each floor level, in circulation spaces between bedrooms and living areas. The Mercury should be ceiling-mounted in the centre of hallways or landing areas, at least 300mm from walls and light fittings. Avoid kitchens and bathrooms where steam can trigger false alarms.