This is out of a Kingsman Vent free logs set manual: WARNING Before installing in a solid fuel burning fireplace, the
chimney flue and firebox must be cleaned of soot,
creosote, ashes, and loose paint by a qualified chimney
cleaner. Creosote may ignite when heated to a high
temperature. Have chimney flue inspected for damage.
If flue system is damaged, you may close the damper if
using as a vent-free system. If you are using the burner
as a vented burner and the flue system is damaged, do
not install the unit.
Check the manual of the vent free log set and verify if there are any other requirements from the Manufacture.