I took the following from the Kidde website. They only answer the phone Mon-Fri, from 8-5, EST. I checked it out because my almost new Kidde CO detector is showing an Error code.
The next time your carbon monoxide alarm has ERR on the display, push and hold the Peak Level button.You will see an E and an O followed by a number.Contact our hotline at 1-800-880-6788 and provide us the error code, along with the model number, assembly number and date of manufacture from the back of your unit.If your unit is under warranty, a replacement will be mailed to you.

NightHawk Model..KN-COPP-3 August 2002 Show up as ERR.... E-09on peak level...Beeps every 30 seconds....

I need to know what the numbers stand for, e.g. 888 and L6?