What smells like gas but isn't gas?

Author: Prof. Sigurd Shanahan PhD  |  Last update: Monday, February 9, 2026

One often not considered source of a “gas-like” smell that can come from your home is bacteria inside of your sink or sewer system. It has a similar smell to the sulfur that is added to gas to give it an odor but is obviously less dangerous.

What smells can be mistaken for gas?

Strong smells in the area, like cooking or chemical odors, can mask the smell of natural gas.

Why do I smell gas but there is no gas?

  • Gas appliances that are not properly ventilated.
  • Gas stove that was not turned off properly.
  • Natural gas odorant that has worn off.
  • Residue build-up in gas pipes or appliances.
  • Plumbing or ventilation issues that allow sewer gas to enter the apartment.

What else could a gas smell be?

Rotten Egg Odors

For safety purposes, utility companies use an additive called mercaptan that gives colorless and odorless gases a smell that is hard to miss. Most people describe this smell as something like rotten eggs, sewage, or sulfur.

What mimics the smell of natural gas?

Natural gas is odorless, but an additive called mercaptan is included to alert people of leaks. Mercaptan has a highly recognizable, sulfur-like, "rotten egg" odor used to help people detect a leak.

Causes When a Car Smells Like Gas but Isn't Leaking

Why do I randomly smell gas in my house?

The presence of a gas odor can indicate a potentially dangerous gas leak, which should be taken seriously. If you suspect a gas leak, immediately evacuate your home, call the gas company or emergency services, and do not attempt to fix the issue yourself.

What does a freon leak smell like?

Freon is generally odorless in small quantities, making it difficult to detect leaks based on smell alone. However, when a leak occurs, a faint, sweetish odor may be noticeable. Some people describe this smell as similar to acetone, nail polish remover, or even chloroform.

Is it a gas smell or something else?

Gas is a naturally odourless substance, but the completely harmless artificial smell is added to make it more detectable. The substance injected is called mercaptan and gives off a strong sulphur-like smell, that some people say reminds them of rotten eggs.

What is septic gas?

Sewer gas is a complex mix of toxic and nontoxic gases that forms when household and industrial waste decay. The concentration of sewer gas typically varies depending on the source. Highly toxic components of sewer gas include hydrogen sulfide and ammonia. Sewer gas also contains: Carbon dioxide.

How do you tell if a smell is a gas leak?

An odor of rotten eggs near an appliance is likely associated with natural gas. Look around the walls for stains; if you notice any discoloration, it could signify a gas leak. You can feel the area for any puffiness, which may indicate excessive heat, which is another indication of a gas leak.

What happens if you keep smelling gas?

A natural gas leak in a house can cause potential fires, and inhaling the gas can cause natural gas poisoning. As with electricity, gasoline and other potentially dangerous energy sources, natural gas exposure must be handled with care.

Will a carbon monoxide detector detect a gas leak?

No, carbon monoxide (CO) alarms cannot detect natural gas leaks. They are designed to detect the presence of carbon monoxide, a poisonous gas formed during incomplete combustion of fuels like oil, gas, propane, and wood.

Why do I feel gassy but no gas comes out?

Constipation can cause poop and gas to get stuck in your intestine. You're taking a medicine that slows your bowels. A digestive system that moves more slowly creates more of an opportunity for gas to build up in your gut. Certain digestive system conditions can slow your bowels, and so can some medications.

What can be mistaken for gas?

Gas in the intestine causes pain for some people. When it collects on the left side of the colon, the pain can be confused with heart disease. When it collects on the right side of the colon, the pain may feel like the pain associated with gallstones or appendicitis.

What does it mean if you can smell gas but there is no gas?

There could be a leaking pipe in the walls or near a vent that is carrying the smell into the room. But my first guess is you have a dead rodent somewhere. This is something I discover regularly when trying to track down a gas smell.

What smells like gasoline but isn't gasoline?

If there is a gas smell but no leaks, it could be the lingering propane odor due to poor ventilation or it coming from your neighbor. The dirty sewage system, contaminated well, or rotten garbage (like veggies, dead animals, residual foods, etc.) might also be the source of the smell.

What does a sewer gas leak smell like?

The smell of sewer gas is often described as a noxious, rotten-egg-like odor. Its sulfuric, foul smell will permeate your entire home if left unaddressed, leading to major health issues down the line. Small amounts of sewer gas usually won't cause any immediate danger—but large amounts certainly will.

What are the three stages of septic?

Septic shock is the last and most dangerous stage of sepsis. Sepsis can be divided into three stages: sepsis, severe sepsis and septic shock. Sepsis: Sepsis is life-threatening. It happens when your immune system overreacts to an infection.

Can sewer gas set off a carbon monoxide detector?

No, it does not. Carbon monoxide detectors DO NOT detect sewer gas. These devices are designed to detect only the presence of carbon monoxide, and thus will not pick up on the other gases that are found in a sewer gas mixture.

What does a carbon monoxide leak smell like?

Carbon monoxide gas is colourless and does not smell, so you cannot tell if it is around you.

What else smells like natural gas in your house?

If your home's boiler, fireplace or central heating system runs on gas, any one of them could be the site of a gas leak. It could also be coming from another source, such as your garbage, sewage or piping, or a dead animal somewhere in your home.

Who do I ring if I smell gas?

1. What should I do if I smell gas or suspect a leak? If you smell gas, call the National Gas Emergency Service immediately on 0800 111 999 or via textphone (minicom) on 0800 371 787.

What does air con gas smell like?

Leaking gas

Old air con systems often use Freon refrigerant, which produces a strong sulphur smell. Not only does this leaking gas smell like rotten eggs, it can be dangerous. Don't put your health at risk, switch off your AC and arrange a professional repair as soon as possible.

What does ether smell like?

Diethyl ether (ether) is notable for its high aqueous solubility compared with other anesthetic ethers. Ether is sweet smelling and mildly pungent; although it can be used for inhalational induction, an ether induction is very slow and risks laryngospasm.

What does propane smell like?

Propane gas has no odor. Propane companies add a harmless chemical called mercaptan to give it its distinctive “rotten egg” smell. All propane pipeline gas in Connecticut is odorized. If you smell gas near an appliance , it may be just a pilot light that has gone out or a burner valve that is open slightly.

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