Keeping a gas heater in proper working order is important to maintain safety as well as to assure energy efficient operation. If yellow flames are observed in a gas heater or other gas appliance, it indicates a problem.
Yellow Flame Cause
When a gas heater has a yellow flame, it is a sign that the gas is not properly burning. Dirt or dust in the burner is the most common cause of the yellow flame, although contaminants in the gas and improperly adjusted burners can also cause the flame to burn yellow. The heater should be cleaned and serviced according to manufacturer directions to correct this problem.
When the natural gas used in the heater is not properly burnt, the heater may produce an excess of fumes. These fumes can be hazardous to persons near the heater. Problems that cause the gas to burn yellow will likely worsen, creating additional fumes from the heater.
The yellow flame in a gas heater is a sign of improper burning, which causes the heater to be less efficient. Heaters with a yellow flame create less heat and use more gas than a properly operating heater.