Natural gas odorant and the potential for odor fade remain an ever-present issue for contractors and others who work on natural gas piping, equipment and appliances.

Even though a distinctive odor is added to natural gas to assist in the detection of leaks, contractors never should rely solely on their sense of smell to determine if a gas leak exists or if natural gas is present, according to a safety bulletin released by Southern California Gas Co., Los Angeles.

Odor fade occurs predominantly in installations of new pipe rather than in existing pipe. It is more pronounced in new steel pipe of larger diameters and longer lengths. However, it also can occur in plastic pipe and in smaller or shorter pipe installations. New pipeline installations or additions of new piping segments may require pipe "conditioning" before it is placed into service to prevent occurrences of odor fade.

Other factors that may cause odor fade include the construction and configuration of the customer's gas facilities; the presence of rust, moisture, liquids or other substances in the pipe; and gas composition, pressure and/or flow. Intermittent, little or no gas flow over an extended period of time also may result in the loss of odorant until gas flow increases or becomes more frequent.

To help ensure a safe operating environment, Southern California Gas offers the following tips for working with natural gas piping.
  • Do not purge the contents of a gas line into a confined space. Any purging of a gas line should be done only in a well-ventilated area or by venting the contents into the outside atmosphere.
  • Always use gas detection equipment or devices during purging operations or when otherwise working on gas piping systems.
  • Do not rely on your sense of smell alone to detect the presence of natural gas.
For more information on natural gas safety, visit