Other than on your trip have you run the furnace again to see if it is still setting off the alarm after 10 minutes? I had a garage heater that if the wind was blowing just right it would force the exhaust back in and set of the alarm.
In our '15 27K the CO detector is on the side of the bed about 12" off the floor, and close to the night stand. Last season we replaced our smoke detector with a combination CO/smoke unit for a little more safety. In our mh there is a 110 outlet on the back side of the bed base that you could plug a household CO detector in to see if it also alarms.
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