One of the biggest maintenance issues in having a gas fireplace is keeping the glass clean. You may notice a white film that builds up on the inside of the glass from time to time. The best thing you can do is to try to prevent it. You may notice a “fog” or moisture on the glass when you first start your gas fireplace. Try to let your fireplace run for a long enough time so all the moisture has a chance to evaporate. The main reason the glass develops a white powdery film is due to moisture in the gas (both natural gas and propane gas) it burns not being completely dried before turning off your fireplace.
The other cause of dirty glass is`1 black soot. Anytime you have black soot on a gas fireplace glass you have a serious maintenance problem. You need to have a qualified service technician service the fireplace. This is an issue that will cause additional problems and just cleaning the glass will NOT take care of it. The soot will continue to build and can cause a dangerous situation.