You can use a vent-free fireplace to provide heat in any room in your home. Vent-free fireplaces provide heat by burning natural gas or propane rather than wood. The flames in a vent-free fireplace should burn blue, although the flames may occasionally burn orange if dirt or other particles get inside the heater and burn. However, flames should not burn yellow. Yellow-tipped flames can cause the appliance to produce unacceptable levels of carbon monoxide. You should immediately open and adjust your vent-free fireplace if you observe yellow tipping.
Turn off gas to the appliance according to the manufacturer's directions. For example, turn off a Williams Blue Flame Unvented Gas Heater by pushing in the appliance's gas control knob lightly and turning it clockwise to the "Off" position.
Open the appliance to access the burner. To access the burner on a Williams heater, lift the screen straight up, pull the bottom of the screen away from the appliance, then pull the screen down. Remove the two screws on either side of the bottom front panel, and pull the panel away from the appliance.
Check the burner for dirt. Remove any dirt from the burner with compressed air, a brush with fine, soft bristles or a vacuum cleaner with a wand attachment.
Reassemble the appliance and turn it back on. The flames should be blue.
Turn the appliance off immediately if the flames continue to burn yellow. Continued yellow flame indicates that the gas regulator is defective. Contact the appliance's manufacturer or a qualified technician for repairs. Do not operate the appliance until the gas regulator is replaced.