On gas fireplaces that are not brand new and are emitting some odor, try cleaning behind the upper and lower louvers. Dust can cause odor. Another source of odor can be the items you have on your mantel. Remove all objects from your mantel and then replace the objects one at a time. A third source of odor can be from the adhesives used in surround materials. This will need to be investigated by your installer. If these suggested sources don’t correctly identify the odor, contact your dealer where the fireplace was purchased and have your fireplace inspected.