First Alert Brk SC9120B (10pack) Smoke u0026 Carbon Monoxide Detector w/ Batt Backup

The alarm features electrochemical CO sensing technology, an ionization sensor for smoke detection, and an 85-decibel alarm. One button silences any nuisance alarms, and also tests detector functions, while lights indicate if the alarm detects smoke or carbon monoxide. The latching alarm indicator automatically identifies which unit initiated the alarm, even after the conditions that set off the alarm have subsided. And an end-of-life signal enhances your safety by letting you know when it's time to replace the unit.