I have a kill switch for my propane detector. But I usually forget to turn it off and it has never been a problem with the batteries.I'm not sure I'd want to turn a carbon monoxide detector off. If CO was present in your RV and you entered, due to it being odorless, you could easily be overcome.
But if you had to, pull the plug or the fuse.
Tony & Ruth........... FMCA#F416727
Newmar Dutch Star 4320, Spartan MM Chassis, Cat C9, Jeep Grand Cherokee,with Hemi, hooked up with a Blue Ox Aventa LX, and Brake Buddy.