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What Does a Natural Gas Leak Smell Like?

lit gas stove

The Bottom Line

Natural gas is a gaseous hydrocarbon mixture with methane serving as the main gas. Methane is a simple asphyxiant that displaces oxygen in the air. If the methane concentration is high enough, the result is hypoxia and asphyxia (suffocation). If you suspect a natural gas leak, leave the building and contact the gas company. If people are sick, call Poison Control.

gas bubbling from pipe
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What is natural gas? Where does it come from?

Natural gas is a naturally occurring gaseous hydrocarbon mixture. It is a greenhouse gas, which means it traps heat in the atmosphere and contributes to global warming. The main component of natural gas is methane. The mixture can contain other hydrocarbons such as ethane, propane, butane, pentane, and hexane. Other gases that might be present include carbon dioxide, helium, hydrogen sulfide, and nitrogen.

Natural gas is formed from the remains of plants, animals, and microorganisms, which are buried under rocks, sand, and the ocean floors. Extreme heat and pressure eventually turn the remains into natural gas, coal, and petroleum. Methane gas then rises through spaces and cracks between rock layers. Wells can collect the underground gas, which is then distributed through pipelines. Natural gas is used for cooking, heating, and the generation of electricity.

What does natural gas smell like?

Methane in natural gas is odorless and colorless. Since natural gas cannot be detected by our senses, a chemical that smells like rotten eggs (mercaptan) is added by your gas company to alert you to the possibility of a leak.

Is natural gas poisonous?

Methane is a simple asphyxiant. When there is natural gas in a room, it displaces the oxygen. This means that you are not breathing in enough oxygen, which can lead to hypoxia (low oxygen level) or asphyxia (suffocation due to lack of oxygen). Natural gas is flammable; when the concentration is 5–15% in air, it can cause a fire or explosion if ignited. The poisonous gas known as carbon monoxide is sometimes formed if there is incomplete combustion (improper burning) of natural gas.

What symptoms are associated with inhaling natural gas?

Symptoms of natural gas inhalation include nausea, vomiting, headache, dizziness, confusion, changes in vision, memory problems, incoordination, feeling sleepy, and coma. A person will become unconscious when the brain does not get enough oxygen, which is followed by respiratory and cardiac arrest. The eyes can feel irritated and dry if the concentration of natural gas in the air is high.

Where is natural gas used in homes?

Natural gas can be found in stoves, ranges, ovens, water heaters, furnaces, clothes dryers, and other household appliances. The gas for these appliances is supplied through pipes from outside the house through a meter that measures how much gas is used. Older appliances have pilot lights, which burn at all times and ignite gas. A safety system should turn the gas off if the pilot light goes out, but a small amount of gas can still leak. However, very old appliances might not have this safety system. Newer appliances use an electric ignition system.

How to detect natural gas leaks in your home

A chemical serving as an odorant, such as mercaptan, which smells like sulfur or rotten eggs, is added to natural gas. If the smell is strong, it is very likely that you have a gas leak. Sometimes an appliance will have a whistling or hissing sound coming from it that signifies that gas is leaking. Depending on the location of the leak, you might also see bubbles resulting from the leaked gas rising through standing water.

Do carbon monoxide detectors detect natural gas?

No, carbon monoxide detectors do not detect natural gas. Carbon monoxide and natural gas are very different chemicals. 

What should I do if I suspect a natural gas leak?

If you suspect a natural gas leak, leave the area. Call for help. Depending on the situation, this may mean calling the gas company, a plumber, or 911. If someone inhales natural gas, or if you have a question about natural gas exposure, help from experts is available through the webPOISONCONTROL online tool and by phone at 1-800-222-1222. Poison Control’s expert guidance is always free, confidential, and available 24 hours a day.
 
Wendy Klein-Schwartz, Pharm.D., MPH
Clinical Toxicologist 

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Poisoned?

Call 1-800-222-1222 or

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Prevention Tips

  • Keep appliances and gas pipes in good working condition. Have your systems inspected at regular intervals.
  • If you suspect a leak, turn the gas off. Open windows and doors and leave the building. Be sure everyone evacuates to fresh air.
  • Do not smoke a cigarette or light matches if you think there is a natural gas leak.
  • Report the gas leak to the gas company.
  • If people are showing symptoms of natural gas toxicity, call 911.

This Really Happened

A family moved into a home with older appliances, including a gas stove and oven. The mother turned on the oven to pre-heat it while she began preparing a meal. Unrecognized by her, the pilot light on the oven was not working properly. She had a cold and stuffy nose and soon began to feel worse with nausea and dizziness, which she thought was due to her cold. She called her husband to help her. Upon entering the kitchen, he immediately noticed the smell of rotten eggs, turned off the oven, and both went outside. He called the gas company to report the leak and contacted Poison Control for advice on how to care for his wife. Since her nausea and dizziness had resolved once she was in fresh air, she was told that she did not need to go in for medical evaluation.

For More Information

Using natural gas safely. American Gas Association. Accessed November 9, 2024.

References

Centers for Disease Control (CDC). Fatalities attributed to methane asphyxiation in manure waste pits--Ohio, Michigan, 1989. MMWR Morb Mortal Wkly Rep. 1989;38(33);583-586.

De-Giorgio F, Grassie VM, Vetrugno G, et al. Homicide by methane gas. Forensic Sci Int. 2012;221:e1-e3.

El Demellawy D, Fernandes J. Suicide by explosion of natural gas: case report and review of the literature. Am J Forensic Med Pathol. 2007;28(1):48-52.

Jo JY, Kwon YS, Lee JW, Park JS, Rho BH, Choi WI. Acute respiratory distress due to methane inhalation. Tuberc Respir Dis (Seoul). 2013;74(3):120-123.

Rossi R, De-Giorgio F, Grassi VM, Pacali VL, Lancia M. An unusual suicide: asphyxia by methane gas. Am J Forensic Med Pathol. 2013;34(2):83-85.

Poisoned?

Call 1-800-222-1222 or

HELP ME online

Prevention Tips

  • Keep appliances and gas pipes in good working condition. Have your systems inspected at regular intervals.
  • If you suspect a leak, turn the gas off. Open windows and doors and leave the building. Be sure everyone evacuates to fresh air.
  • Do not smoke a cigarette or light matches if you think there is a natural gas leak.
  • Report the gas leak to the gas company.
  • If people are showing symptoms of natural gas toxicity, call 911.

This Really Happened

A family moved into a home with older appliances, including a gas stove and oven. The mother turned on the oven to pre-heat it while she began preparing a meal. Unrecognized by her, the pilot light on the oven was not working properly. She had a cold and stuffy nose and soon began to feel worse with nausea and dizziness, which she thought was due to her cold. She called her husband to help her. Upon entering the kitchen, he immediately noticed the smell of rotten eggs, turned off the oven, and both went outside. He called the gas company to report the leak and contacted Poison Control for advice on how to care for his wife. Since her nausea and dizziness had resolved once she was in fresh air, she was told that she did not need to go in for medical evaluation.