What to Do If You Have a Natural Gas Leak

Pair of hands opening window to allow fresh air in

The Spruce / Michelle Becker

Knowing how to handle major utilities in an emergency such as turning off the water and shutting off the electrical power is essential knowledge for any homeowner.

The same holds true for natural gas or propane as a utility. Natural gas is a combustible mixture of hydrocarbon gases, and in its pure form, it is colorless, shapeless, and odorless. The characteristic “rotten egg” odor we are used to is an odorant added by the utility company called mercaptan and is added as an aid in detecting leaks.

Leaking natural gas may present hazards including:

  • Fire
  • Explosion
  • Asphyxiation (because natural gas displaces oxygen in confined spaces)

Some signs of a natural gas leak inside your home include:

  • Distinctive "rotten egg" odor
  • Hissing or blowing sound

Some signs of a natural gas leak outside your home include:

  • Dead or discolored vegetation in an area that has otherwise healthy plants;
  • Dirt or dust that is blown out of a hole in the ground;

Natural Gas Versus Propane or LPG

Natural gas is not LPG (Liquefied Petroleum Gas). Natural gas is almost 40 times lighter than air, but LPG gasses (e.g., propane) are heavier than air. As a result, propane gas will collect in low places, and natural gas will rise and collect in high places.

Combustibility of Natural Gas

Natural gas by itself cannot burn and must be mixed with air to ignite. But to ignite, it must also have an ignition source like a pilot light, match, lighter, or–in some cases– an electric arc from a light switch, motor, or old doorbell.

What to Do if Natural Gas Has Ignited

Interestingly, natural gas that is already burning will not explode. If you have a situation where natural gas does ignite, it is recommended to let it burn. Do not attempt to put out the flame as this may fill the home or room with natural gas, creating a more dangerous situation.

What to Do If You Smell Natural Gas Inside the Home

Small Leak: If you suspect a small natural gas leak, then proceed as follows:

  • Open all doors and windows.
  • If it is possible, check to see if appliance burners are fully off and any pilot lights are lit.
  • Call the utility company and follow their directions.

Large Leak: If the gas odor is pronounced and strong and you suspect a possible significant natural gas leak, or if you have any uncertainty at all about the size of a leak, then proceed as follows:

  • Do not try to find the source of the natural gas leak.
  • Do not try to shut off any gas valves or appliances.
  • Do not operate any electrical or mechanical devices (including phones or computers).
  • Do not start any vehicles or use a garage door opener.
  • Leave home and remove all occupants.
  • Call the utility company and follow their directions. Do not re-enter the home or return to the area until the utility company employee says it is safe.
  • In the case of a suspected gas leak, only turn off the shutoff valve if the meter and shut-off valve are located outside the home, no gas can be smelled at that location, and the utility company says it is safe.