How To Detect A Natural Gas Leak

• How to detect a natural gas leak

• The distinctive odor of natural gas
• What to do if you suspect a natural gas leak
• Odor fade (loss of odorant)

How to Detect a Natural Gas Leak

It’s important to know that any of the following signs may indicate the presence of a gas leak:

• The distinctive odor of natural gas.
• A damaged connection to a gas appliance.
• A hissing, whistling or roaring sound near a gas appliance or pipeline.
  • Special markers show the location of most major pipelines.
• Dead or dying vegetation in an otherwise moist area over or near pipeline areas.
• A fire or explosion near a pipeline.
• Dirt or water being thrown in the air.
• Exposed pipeline after an earthquake, fire, flood or other disaster.

The Distinctive Odor of Natural Gas

Although a distinctive odor is added to natural gas to aid in the detection of leaks, you should not rely on your sense of smell alone to determine if there is a gas leak. Some persons may not be able to smell the odor because they have a diminished sense of smell or because the odor is being masked by other odors in the area. In addition, certain conditions, such as odor fade (loss of odorant) may cause the odor to diminish so that it is not detectable.

• More on odor fade (loss of odorant)

What to Do If You Suspect a Natural Gas Leak

If you smell a natural gas odor, hear the hissing sound of gas escaping or see other signs of a leak:

• REMAIN calm.
• DON'T light a match, candle or cigarette.
• DON'T turn electrical appliances or lights on or off.
• From a safe location, call SDG&E at 1-800-411-7343 24 hours a day, seven days a week; or call 911.

Odor Fade (Loss of Odorant)

Odor fade (loss of odorant) can cause the odorant to diminish so that it is not detectable.  Do not rely on your sense of smell alone to detect the presence of natural gas.

Odor fade is caused by physical and chemical processes.  It occurs predominantly in installations of new pipe rather than in existing pipe. Odor fade is more pronounced in new steel pipe, and in pipe of larger diameter and longer length. However, it can also occur in plastic pipe, and in smaller pipe installations. In addition, if a natural gas leak occurs underground, the surrounding soil may cause odor fade.

New installations or additions of pipe may require the conditioning of the pipe before it is placed into service to prevent odor fade. Other factors that may cause odor fade include:

• Construction and configuration of the customer’s gas facilities.
• Presence of rust, moisture, liquids or other substances in the pipe.
• Gas composition, pressure and flow. 

Intermittent, little or no gas flow over an extended period of time may also result in the loss of odorant until gas flow increases or becomes more frequent.

Remember, do not rely on your sense of smell alone to detect the presence of natural gas. For more information on odor fade, please refer to our Safety Bulletin. If you have additional questions or concerns regarding odor fade, call SDG&E anytime at 1-800-411-7343 or contact a licensed, qualified professional.

Last updated: June 10, 2009