Thanks all for the input. We were using it and it seemed to be working fine except that when the heater stopped you could feel cold air entering the inside.
We WILL STOP using it Immediately! The CO2 detector never went off so I think we were fine but won't take any chances.
We will take it into a dealer next time we get up there. I didn't think I should be able to see through to the outside cover. I was also wondering why there was no return air filter in it like a house heating system. I will let you all know what the final answer is.
