Early morning, I heard our CO detector go off, a few days after hubby had put in a new battery, so we both thought we had CO in the house. Opened all the windows, turned off the furnace, and got out of there. We've since found out the sound we had heard wasn't the true CO warning, but not the low-battery warning, either. Don't know why it sounded off, but there was no CO in the house. It had gone "te-te-te-te-" in rapid fire, while the true CO warning is a continuous loud shrieking that doesn't shut off. We didn't know that, at the time. Our heating guy seems to think a little dust got into the unit, which is very sensitive.

We have since installed two other CO detectors, and if there's a problem, they should ALL go off.

Awhile back, we had a smoke detector that we finally had to deactivate because it wouldn't stop falsing.

So, I question the usefulness of some of this technology if it isn't going to give us accurate warnings?