Well,.........We have two CO detectors on board and neither warned us of an issue. Returning to the boat after a few days I noticed a strong odor as soon as I opened the door. Checked the ER where it was noticeably stronger. Found one 6 year old 8D just beginning a thermal runaway and disconnected it with disposal following. Each detector is a different brand. Neither gave any warning while aboard a few days earlier, or when the action was really ripping. Batteries were up to snuff in both, so very curious after reading this thread. Junk em' or keep em'?