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Properties of Natural Gas

Natural gas is non-toxic, colorless, odorless and combustible. For detection and safety, Washington Gas adds an unpleasant, sulfur-like odorant called mercaptan to the majority of natural gas traveling through its pipelines. Mercaptan gives a strong odor so you will be able to detect escaping natural gas. Gas traveling through a small portion of our transmission pipeline is not odorized. Because gas is lighter than air, when released, it rises and mixes with the air. Outdoors, it dissipates into the atmosphere. 


When Natural Gas Burns 

Natural Gas Flame

Natural gas burns only when it is mixed with air in certain concentrations and ignited—by a spark, a match or some other source of heat. Gas appliances are designed to mix natural gas with air at a controlled rate.

The burner flames from your gas appliances should always be blue and steady. The bright blue color shows that the correct amounts of gas and air are combining for safe operation. Yellow or wavering flames indicate that gas is not burning completely and repairs or adjustments are necessary.

However, gas fireplaces, which may have a luminous yellow flame, still burn completely without the formation of carbon monoxide. These fireplaces have a safety device that automatically turns off the unit if the oxygen level falls below what is needed for proper combustion.

Some gas appliances have pilot lights that burn continuously, and gas appliances always produce flames when operating, even if you can’t see them.


Indoor Air

Gas appliances and fireplaces use oxygen from the air to operate. When a home is sealed tightly, the oxygen inside can be used up and not replaced fast enough. The lack of air can cause incomplete burning, allowing carbon monoxide to form. Never enclose gas furnaces, water heaters or dryers in a closet or small room without providing openings for air circulation as required by local and state code.



Indoor air quality can be affected when the products of gas combustion are not vented properly. If your appliances require venting through metal pipes-- also known as flues-- a match test can be used to find out if your venting is effective. Once the burner is lit and operating normally, wait approximately 30 seconds and then hold a lighted match just below the flue-diverter on water heaters, furnaces and boilers.

If the flame leans towards you, flutters downward or goes out, the system is not drawing combustion particles outside through the vent or the flue. If you notice these signs, turn off the appliance, air out the building and call a licensed natural gas contractor immediately to inspect the equipment.

If the appliance is in an area with an attic fan, kitchen fan or bathroom fan, the fan can set up vent or flue back drafts. Have a licensed contractor check your venting.