Kidde KN-COB-B-LP2 Carbon Monoxide Alarm Battery-operated carbon monoxide alarm; no hardwiring required Alarm will sound when dangerous levels of CO are detected Test/Reset -Tests CO alarm circuit operation and allows you to immediately silence the alarm Battery Lockout System deters covering battery compartment without installation of batteries Low Battery Hush silences low battery chirp warning for up to 12 hours in order to maintain protection without having to replace the batteries at an inconvenient time