First time out, first night out, the carbon monoxide alarm went off. Scared the wife, but I just turned on the bathroom ceiling exhaust fan for a couple of minutes, and left a window open. Did not re-occur.
Since ours didn't originally come with one, I added it, and mounted it adjacent to the propane detector, reason being that home units are plugged in at about eighteen inches off the floor. I suspect it didn't like the mounting location, as they are supposed to be mounted high, not low. Turns out, CO is slightly LIGHTER than air.
It's now been removed, and awaiting a high re-location before the next outing.