WIRELESSLY INTERLINKED FOR COMPLETE HOME SAFETY: Connect up to 20 BLACK+DECKER alarms using advanced RF10-PRO radio frequency technology. When one alarm triggers, all connected devices, including smoke, heat, and carbon monoxide alarms, will sound simultaneously for fast, whole-home alerts. 10 YEAR SEALED LITHIUM BATTERY: Tamper-proof, long-life lithium battery powers the alarm for its entire 10-year lifespan. The alarm will indicate when it reaches the end of life, no need to replace or maintain batteries. ACCURATE CARBON MONOXIDE DETECTION: Equipped with a high-quality electrochemical sensor that quickly identifies dangerous CO levels. Emits four loud 85dB alerts and a flashing red LED to warn you immediately of carbon monoxide presence. EASY SET UP GUIDE: Slide the alarm downwards onto the activation base plate and you will hear the alarm CHIRP once and flash 5 times. Press and RELEASE the test button for 3 SECONDS and the alarm will sound after release. The activation base plate must be inserted for the alarm to work. TRUSTED QUALITY & CERTIFICATION: Includes alarm memory indicator flashing for 72 hours after CO detection. Fully compliant for residential and rental properties across England, Scotland, and Wales. Kitemark certified by the British Standards Institute (BSI) to BS EN 50291-1:2018 and BS EN 50291-2:2019.