It's just a carbon MONOxide detector, no such thing as a carbon DIoxide detector in RVs. If there was, it would be going off every time you open a pop can or exhale. Carbon dioxide makes your drinks fizzy, carbon monoxide will kill you. Yours is probably a combination CO/Propane detector, and is hard wired into the trailer's 12 volt system.
These devices have set life-spans, something like 5 years or so. If it goes off without any known reason, it's probably time to replace it. There's a date on the back, "Replace by XXXX". Your local RV dealer will have the needed parts, and swapping it out is easy if you're halfway handy.
Geoff & Jill
& Sierra, the little white monster
2013 Ford F-150 XTR SC Ecoboost
2015 Jayco Jay Flight 24FBS