I'm glad you resolved it.
Bear in mind that many spilled fluids will trigger the CO alarm: wine, booze, cleaners, and so on. Anything with VOCs that can evaporate is likely to trigger the alarm.
Ask me how I know.
An open bottle of wine in our fridge tipped on its side. The cork was loose, but did not fall out. Approximately 1/4 cup of wine (+/-) ran out of the fridge onto the floor. As luck would have it, the CO alarm was right next to the fridge.
After a panicked removal of both propane tanks, the alarm continued. We cleaned up the wine, and all was well.