Carbon Monoxide/LP detector issue

Thanks for the replies. The camper is new and it still has the new smell. When the outside temp gets high and the sun causes the interior temp to get very high there is a slight glue or something smell that you can barely smell. From what some of you are saying this may be the cause. Today I left the camper plugged into my house with only the air on set at around 77* and the detector did not go off. I unplugged the camper from the house tonight to see if it is alarming in the morning. I may get a thermometer and place it in the camper so I can monitor the temp on hot days to see how hot it is getting in it. Again there was no issue with this until the outside temp started reaching the low 90's causing the camper to get very hot inside. We don't have a shed for it yet but will be placing a cover over it this week. maybe that will help some. If not i'll just keep the air going at around 80* inside on the very hot days.
And yes this is a combo unit placed about 4" off the floor. One thing I wondered about could the black water tank which is empty be giving off some fumes on the hot days when the inside of the camper gets very hot causing the alarm to go off? I don't notice any fumes from the tank but just thought there may be something there. Again thanks for your replies.