Kidde KN-COSM-B Battery-Operated Combination Carbon Monoxide and Smoke Alarm with Talking Alarm *4-Pack* Combined Carbon Monoxide and Smoke Alarm - A single unit can be installed where previously, two were Hush Feature - Temporarily silences nuisance alarms. Voice Alarm - Announces the hazard type detected thereby helping to speed up the correct reaction Uses 2 AA Batteries (Included) Low Battery Warning - The unit warns of a low battery condition by announcing "low battery"