Worry-Free Combination Smoke & Carbon Monoxide Alarm with Lithium Battery P3010CU Combination Smoke and Carbon Monoxide Alarm  Smoke and CO sensing technologies work together to detect real fires faster and reduce nuisance alarms. Voice Alarm  Announces the hazard type detected thereby helping to speed up the correct reaction. Alarm announces Fire! when a smoke or fire hazard is detected and announces Warning Carbon Monoxide when a CO hazard is detected. Sealed-In Lithium Battery  Sealed-in lithium power supply; no battery replacement required over the 10 year life of the alarm. Eliminates worry about battery removal or unauthorized deactivation of alarm. Photoelectric Sensor  Smoke alarm contains advanced photoelectric sensor that may detect visible particles (associated with smoldering fires) sooner than ionization alarms. Self Activation  Alarm automatically activates when attached to the mounting bracket.