The Vent-Free log sets are designed and manufactured to be operated in a wood burning fireplace, in good working order, with the damper closed or in a manufactured Vent Free firebox. Vent Free gas logs can be used in an existing Masonry or Prefabricated wood-burning fireplace with the damper closed. With the damper closed all the heat will travel to the top of the firebox and then out of the front of the fireplace. Shop Vent-Free log sets.