The House Detective by Barry Stone, Certified Home Inspector
Dear Barry: We are concerned about the safety of our ventless gas fireplace. We use it a lot, and a black film has recently appeared on the glass panel, as well as on our windows. What should we do? Barbara
Dear Barbara: The first think to do is stop using the fireplace and report the problem to a qualified fireplace specialist for evaluation and repair.
When a gas-burning fixture produces a black residue, that is a symptom of incomplete combustion and faulty exhaust venting. It means that combustion byproducts are venting into your home, and this is potentially dangerous, depending on whether these byproducts include carbon monoxide.
After your fireplace is professionally serviced, read the owners manual before resuming use. The manufacturer’s instructions may advise not using the firxture for periods of more than two hours. The manual may also recommend that a nearby window be kept open while the fireplace is in use to dilute exhaust with fresh air.
Ventless gas fireplaces are vigorously defended by their manufacturers as being incapable of abnormal combustion. In past articles, I’ve expressed the view that no manmade product is, or ever can be, 100 percent foolproof. Your situation appears to support that opinion.