I've got this one as well in my RV8. I tested to make sure it works with candles, car exhaust, and it trigged once that I can recall when I was waiting to line up with wind at my back. It seems to work well. Normally it shows 0, which is what I want. I power it on for the calibration step after moving the aircraft out of the hanger with the canopy open and of course engine off.
I just saw an EAA webinar (https://eaa.org/Videos/Webinars#
) with faast credit about CO and it was scary - both the story the presenter told, and the fact that he says his CO detector "only" runs at a constant 20 now after repairing his exhaust system. If mine showed anything above zero during normal operations I'd be looking for leaks.
Perhaps I'm being a bit too persnickety, but CO has caused many pilots to have a very bad day.