The thermocouple on a gas fireplace may eventually become clogged with dirt and soot, which can reduce the effectiveness of the thermocouple and may eventually prevent the fireplace from lighting as expected. Cleaning the thermocouple is a pretty simple process but should only be done when the fireplace is turned off and is completely cool. Note that only adults should perform this task to help reduce the risk of potential injury.
Turn off the fireplace gas valve and remove the front panel from the fireplace. Some panels have a screw on each side that needs to be removed and other panels lower on a hinge.
Find the thermocouple, which is located next to the pilot light and looks like a small straight pipe.
Use a can of compressed air to gently blow away any dust and dirt from the thermocouple.
Wipe away any remaining dirt or soot on the thermocouple with a clean, dry cloth.
Close the fireplace access panel and restore the gas supply to the fireplace.