Kidde KN-COP-IC Hardwire Carbon Monoxide Alarm w/ Battery Backup & Digital Display Digital display displays the level of carbon monoxide the unit is sensingBattery pull tab eliminates battery installation time and keeps battery freshPeak level memory displays the highest CO concentration measured since the last resetTamper resist locking pin helps deter alarm tampering and theftKidde"s carbon monoxide alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards Need more information on this product? Click here to ask.