Make personal safety your priority with this durable combination smoke & carbon monoxide alarm, with a ten-year product life. This unit comes equipped with a sealed-in lithium power supply that lasts the entire ten-year life of the alarm & eliminates concerns about battery removal & unauthorized alarm deactivation. It's quick & easy to install; alarm automatically activates when attached to the mounting bracket. Smoke alarm contains photoelectric sensor that may detect visible particles associated with smoldering fires sooner than ionization alarms. Includes a test / hush button that tests alarm circuitry & temporarily silences nuisance alarms. Rapidly flashing LED lights alert users if alarm has sounded since the last time the test / reset button was used. End of life warning alarm chirps every 30 seconds when unit is in need of replacement, but can be silenced three days at a time for 30 days to allow time for replacement. Power Source(s): Lithium-Ion Battery; Mounting: Ceiling.