UPDATED: Carbon monoxide alarm goes off while baking in oven

UPDATE: After taking the TT to get some service done, it was found that the flap on the rear of the RV that vents gasses had closed. The FLAP is about 9 feet high from the ground, not at eye level, not even near eye level. The flap is made to be open, but also closed when not in use. This had closed and the little buttons that keep it closed were indeed flipped over it keeping closed. I never saw this vent before. The RV service tech said 99% of people he talks don't even know this flap exists outside the rig.