The Combination Smoke & Carbon Monoxide Alarm with Voice & Location is easy to program with 11 pre-programmed home locations. The voice alarm not only tells you what part of the home is in danger; but whether the danger is smoke or carbon monoxide. Photoelectric smoke sensor reduces nuisance alarms from cooking smoke or shower steam and electrochemical carbon monoxide sensor is combined for increased accuracy. There is a mute button to silence any nuisance alarms that may occur. The single button tests all alarm functions. The batteries are easy to replace and there is no need to remove the alarm from the ceiling to change a battery. Meets UL standards.