How to detect natural gas

Natural Gas Leaks

There are a number of different ways to identify a potential natural gas leak.


If you see:

  • A damaged connection to a natural gas appliance
  • Dirt, water or debris being blown into the air
  • A dry patch of grass in your yard (in an otherwise moist area)
  • A fire or explosion near a pipeline
  • Exposed pipeline after an earthquake, fire, flood or other disaster


  • If you hear an unusual sound, such as a hissing, whistling or roaring, near a natural gas line or appliance.


  • If you smell the distinctive odor of natural gas, often described as a sulfur-like odor.
  • Note: some people may not be able to smell the odor for a number of reasons (see below).

Don’t Rely on Just Your Nose

Although a distinctive odor is added to make natural gas easy to recognize, you may not be able to smell leaking gas if:
  • You have a diminished sense of smell
  • You’re experiencing odor fatigue (normal, temporary inability to distinguish an odor after prolonged exposure to it)
  • You have a physical condition such as a common cold, sinus condition or allergies
  • You use tobacco, alcohol, drugs and certain medications
  • The odor is masked or hidden by other odors that are present
  • Pipe and soil conditions have caused odor fade (see below)

Odor Fade

Sometimes physical and/or chemical processes can cause a loss of odorant in natural gas, making it undetectable by smell. Odor fade can be caused by adsorption, absorption, oxidation or any combination thereof.

Odor fade is more likely to occur in the following situations:

  • In new, steel pipe that has been recently manufactured or hasn’t been used for odorized natural gas before
  • In natural gas piping systems using higher gas pressure, and when natural gas flow is limited or intermittent
  • In the presence of rust, mill scale, moisture, air, cutting oil, pipe thread compound, liquids, condensates and other substances

Because of the possibility of odor fade, it's important to not rely only on your sense of smell to be alerted to a natural gas leak.

For a printable copy about odor fade and safe purging practices, see our Safety Bulletin.

If you have additional questions or concerns regarding pipe conditioning or odor fade, call us at 1-800-427-2200 or contact a licensed, qualified professional.

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:

  • IMMEDIATELY EVACUATE the area, and from a safe location either call 911 or SoCalGas at 1-800-427-2200
  • DON'T smoke, or light a match, candle or other flame.
  • DON'T turn electrical appliances or lights on or off, operate motorized equipment or vehicles, or use any device that could cause a spark.


24 hours a day, seven days a week; or call 911.