I have this one from AliExpress too.
I use it in a room with a pallet heating boiler. Even when the boiler is not active for a long time and windows are open (there should be no extra CO levels) the sensor is beeping from time to time. It is a single beep every few minutes. No regular pattern
I was thinking that it is a warning for higher CO levels but I am not sure. I do not use a battery but an adjustable voltage adapter from 12V to 9V so I do not need to replace batteries. Anyone using this one?