I've seen those - I think those were not factory - but not sure - from what I remember they are not vented - not a good thing.
I suppose you could open it up - look over the burner and heat exchanger and look for cracks and stuff, turn on gas and check for leaks with that soapy stuff - however, if it were me, I would probably not use it. I certainly would not use it when sleeping.
1956 Flying Cloud
Four Corners Unit
Albuquerque National Balloon Fiesta
Vintage Trailer Academy - Formerly the original