Factory built/prebabricated fireplaces – All manufacturers require that the glass doors be fully open when operating the fireplace with gas logs. Not partially open, FULLY OPEN. Partially opened doors as well as closed doors tend to cause spillage of the gases into the house.
Masonry fireplace – In this case, the doors are not a included part of a fireplace system, rather an accessory. They are a separate item placed over the opening of the fireplace. In some cases, they may have some inlet grills that allow enough air to enter into the fire chamber, even with the doors closed. Our recommendation still remains that you operate the fireplace with the glass doors fully open.