This BRK SC9120B smoke and carbon monoxide alarm is a 120 volt wire-in single and/or multiple station combination smoke and carbon monoxide alarm designed for residential and institutional applications including sleeping rooms of hospitals, hotels, motels, dormitories, and other multi-family dwellings. The alarm features an end of life signal which provides audible notifications when the alarm needs to be replaced. Two locking features prevent battery theft or theft of the unit. This alarm also has an 85-decibel alarm and functions at temperatures from 40 to 100 degrees Fahrenheit and up to 95% humidity. Listed to UL 217 and UL 2034 standards, this fire and carbon monoxide is a great choice for keeping your home safe.