This Battery powered ionization smoke alarm is best at detecting fast flaming fires. The alarm features a Mute/Silencebutton to quiet false alarms. A single button also tests alarm functions. The Easy access battery drawer allows batteries to be changed without removing the alarm from the ceiling. Loud 85-decibel.Dimensions: 2" x 5-1/4" diameter.10-year limited warranty. 9V Battery Included.