Our new home was finished in Sept 2010 & the vented (outside wall) gas (propane) fireplace first used in Oct 2010. We experienced the stinky burn off and a lot of 'haze'... so bad that after 20 hrs. of burning while we were not living there, the entire house had to be aired out, and it still didn't correct the issue. The company who sold us the fireplace/logs said before we attempted the burn off that the resulting fumes were not dangerous to us and should burn off at 9-10 hours. Right. We had the system checked out by the installer and the builder... all appears to be in order yet upon trying one more time, there came the light haze and upon entering the room (we left the door shut... so we didn't have to air out the entire house again if it failed) we noted the smell and this time, a significant lack of oxygen in the room.