Universal Security Instruments CD-9000 9-Volt Battery-Operated Carbon Monoxide Alarm The optochemical sensor technology makes this unit resistant to nuisance alarms, extends sensor life and provides fall-safe notification 9-Volt alkaline battery operated carbon monoxide alarm, (battery included) Fast and easy to install, with no wiring required Audible low battery warning; alarm and power test buttons The alarm sounds with its loud 85 decibel horn and the red LED indicator flashes