CO-detector with interlink capability and a built-in 10-year lithium battery. Visible easy-to-use test key. Carbon Monoxide (CO) is produced when fossil fuels do not burn completely or are exposed to heat. These fuels include wood, coal, charcoal, oil, natural gas, gasoline, kerosene and propane. The CO-detector reacts when CO concentration reaches certain thresholds and provides a local audible alarm (85 dB) and triggers a call to the monitoring centre via the social alarm unit. If the CO-detector is interlinked with other detectors the alarm sound in all detectors. The CO-detector can be connected to Careium’s social alarms and carephones to create a secure home environment. It can interlink with Careium Smoke i10, Heat i10, and additional CO-detectors for maximum security.