Place a drop cloth on the floor and open windows in the room. Cover your nose and mouth with the face mask.
Clean out the inside of your gas fireplace. Brush off the walls and use a sponge and grease-cutting soap to scrub the walls. Rinse the walls with clean water and allow them to dry completely.
Apply the firebox paint to the interior of the gas fireplace with the paintbrush. Paint the floor, sides and back of the fireplace, starting at the top and working your way down to the bottom. You don’t have to paint any portion of the fireplace that you can’t see from the outside.
Allow the paint to dry for 24 to 48 hours before starting a fire in the gas fireplace.