The Child Awakening Combination Smoke & Carbon Monoxide Alarm with Voice Location Feature is more effective at waking up sleeping children. They are 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 with no need to remove the alarms from the ceiling to change a battery. Meets UL standards.