Rear projection toshiba picture and color too dark

I have had this situation with this tv once before and i really didn't catch it until this time. i heat my home with a propane stove and it went crazy one night and smoked up my house i noticed the tv picture kept getting darker and noticed the heater flame too high. i pulled off the front cover and guess i knocked off some soot or something as the picture got better but not like it was. i had this same problem fixed under warranty almost a year ago and i cannot for the life of me think of what was replaced. i just wonder if there is some part i could use some compressed air and spray it maybe clean off the bulb?...