Check the listing for details. Kidde Nighthawk Plug-In Carbon Monoxide Alarm + Battery Backup KN-COPP-3. Color: White, Condition: Open box. Listed at 20.99 USD. Kidde Nighthawk Plug-In Carbon Monoxide Alarm + Battery Backup KN-COPP-3 Comes in Bulk Packaging Peak level button – Displays the peak CO level recorded by the alarm since it was last reset or unpluggedTest button functions – Tests the unit for proper operation and resets the carbon monoxide alarmLED operation – Blinking dot in lower right corner of display denotes normal operationTen years after the initial power up, this alarm will “beep” two times every 30 seconds to indicate that it is time to replace the alarm.Note: This CO alarm is not battery operated. However, these alarms are equipped with 9 volt battery backup – the 9 volt battery is to supply short term back-up during a power outage.Power source: 120VAC. Temperature range-40˚F (4.4˚C) to 100˚F (37.8˚C). Humidity range-5%-95% relative humidity (RH) Easy to Read DisplayThis plug-in CO alarm is designed with a clear, visible readout that will accurately record the levels of carbon monoxide present so that you can quickly know if an area of your home is at risk. It measures CO levels between 30 and 999PPM, and the display will also indicate if the battery needs to be replaced.Unbeatable ProtectionAlways protect your family and home by making sure you are prepared for any emergency or hazard with the Kidde plug-in carbon monoxide detector. This CO meter uses an electrochemical sensor and features a clear digital display screen to monitor and record any CO levels in any room of your house. This sensitive and clear detector will leave you confident that you are protected against carbon monoxide.Peak Level Memory FeatureDisplays the peak CO level recorded by the alarm since it was last reset or unplugged