8 Pack Of Kidde KN-COSM-B Battery-Operated Combination Carbon Monoxide and Smoke Alarm with Talking Alarm Talking alarm announces the hazard type detected, helping to speed up reaction time A single unit can be installed where previously two were needed Battery safeguard ensures the unit cannot be accidentally mounted without batteries installed Test-reset button tests alarm circuitry and triggers the voice announcement Meets requirements of Underwriters Laboratories (UL), an independent facility that tests products for safety compliance