What Causes a Gas Fireplace to Explode?

Faulty Gas Valves

• Although rare, gas fireplace explosions can be caused by faulty gas valves that leak flammable gas into the air. This happens when the valve's "On/Off" switch fails and continues to seep gas into the fireplace pilot light area. A spark or flame can cause the gas in the air to immediately catch fire, and create a powerful explosion.

Chimney Design

• Other causes of explosions in gas fireplaces may be chimney and flue design. The University of Nebraska publication “Chimneys: Their Installation and Upkeep” states that some chimneys designed for natural gas are unable to withstand high temperatures, contributing to soot and creosote buildup. Creosote — a black, sticky substance formed from liquefied gas — is the leading cause of chimney fires, according to the Chimney Safety Institute of America. Double venting systems exacerbate the issue and can cause gases to back up into flues connecting to other stoves or furnaces. The resulting backup causes an explosion or leaks carbon monoxide into the home.

Plugged Burners

• Paint and building materials can form over the burner hole port. Ceramic coals or mineral wool may inadvertently be placed over the ports, creating a blockage and unbalanced flame. Consequently, the plugged burner hole can delay fireplace ignition, and cause gas in the fireplace to explode.

Precautions

• Call a professional service technician to remove creosote buildup from chimneys and fireplace walls. Gas valves and hose connections leading to the fireplace burner and tank should also be inspected by a professional technician. Moreover, check for cracks in the flue lining and firebox, and look for signs of rust and corrosion. Your fireplace should also be equipped with a thermocouple, which shuts off the gas in case the pilot light is extinguished.