Kidde Carbon Monoxide Alarm with Digital Display/Plug-In KN-COP-DP-LS Digital reaout - from 30-999 PPM provides continuous montoring of CO levels Works during power outages - when used with a 9V battery (included) Peak level memory - recalls the highest danger level detected Test/Reset button - allows you to immediately silence alarm and test alarm electronics Loud 85 decibel alarm