[I need help]

I am a Firefighter and we have recently been receiving calls for CO detectors going off. Sometimes we narrow to cause down to a car battery in the basement that is used as a battery back-up for the sump pump. The battery is marine grade and enclosed in a plastic case with small air vents. when we put our detectors up to the vents we start to see the CO levels rise rather quickly. So my question is can the battery be emitting CO or some other chemical that would set off the detector?

[Borek]

Strange, as far as I know battery chemistry (and I suppose these are just lead batteries?) they can emit some amount of hydrogen, but no carbon monoxide. The only thing I can think off is that the acid is contaminated with some organic stuff and CO is emited after dehydration, but that's a long shot.

Still, I don't know everything, so don't treat this answer as the conclusive one.