Comfort and Safety Carrier's Carbon Monoxide Alarm uses sophisticated electronics and unmatched sensor technology to detect and record the levels of CO circulating in your indoor air. You can monitor the current CO level in your home on a large, easy-to-read digital display. When dangerous levels of CO are present, a loud, audible alarm alerts you and your family, automatically - The Carbon Monoxide Alarm's peak level memory allows health care professionals to quickly assess the level of exposure in the event of an alarm. - A rechargeable lithium ion battery ensures continued detection and warning even during a power outage. - For peace of mind, you can check to see if your CO alarm is functioning properly with the simple push of a button. - Carrier recommends checking the alarm weekly and having it professionally inspected on an annual basis.