In some applications, a chimney may not be possible or desired. In these cases the installation can be achieved without the need to run the vent through the roof by using our vent free zero clearance box. This firebox is the same configuration as our vented box, but the burner does not require a chimney. Instead the heat is run off the top of the zero clearance box throuth two small vents to the sides of the chase.. Check with the building authorities in your area to insure that the vent free technology is permissable.