Ours went off last night-scared the crap out of us. We called the FD-they sent a crew who had their own meter-they checked the basement, ground floor, and upper floor. Thank God, they detected no CO.
The detector was 5 years old (should have a 8 year service life, and had a fresh battery). According to the fireman , these things can fail at any time-the thing was, it didn’t go into “fail” mode (a series of short beeps-it went into warning mode (4 short beeps, followed by a steady wail. I’ll buy a new one tomorrow-but scarey all the same!
Certain odors/chemicals can cause a CO detector to record false high readings and also permanently damage them. A few years ago my mother did a home perm (only elderly women use those still I think) and a few hours later the fumes caused the CO detector to go into warning mode. The CO detector recorded dangerous levels of CO, over 250 ppm. Fire dept and gas utility were called and neither found high levels of CO and determined her home to be safe. The fire dept. gave her a new CO detector.
Mine died too. It was less than a year old.
Are you in the snowstorm affected area? If so, maybe you really did briefly have high CO caused by fast accumulating snow.
We had one go off years back. We called the company, gave them a number on the plate, and it turned out to have reached a built in expiration date.