All catalytic heaters burn oxygen, so they must be vented. Some are vented with a small fan. I would assume by it's age yours is not.
So IF it lights and gives off heat you need to leave a vent or window open a crack to allow for the buildup of bad gasses to escape. These heaters were not designed to keep the coach toasty warm, they are for when you need heat and do not want to use 12 VDC power. Or if you are trying to take the "Chill" off the coach they work well. I know many members have them and use them regularly.
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato