"FIRST ALERT" BRK SMOKE & CARBON MONOXIDE DETECTOR *For bedroom, hall, basement, family room *120V AC 60 HZ with 9V battery back-up (included) *Ionization smoke sensor *Intelligent sensor reduces nuisance alarms *2 silence features: temporarily silence low battery chirp for up to 6 hours and silence an unwanted alarm for several minutes *Tin oxide sensor permanently stores highest c/o reading *Automatically performs internal test *Interconnect up to 12 units *Quick connect plug with 8" pigtails *Universal mounting bracket with screw slots *Boxed *Discovery NBR, SUP