Can gas leak smell come and go?

Author: Lucio Crist IV  |  Last update: Monday, March 16, 2026

Natural gas leaks are particularly likely to cause smells in small, enclosed areas where gas can build up. If the leak is outside, the smell may seem to come and go as the breeze blows it away. The other big sign to look out for is a strange noise.

Can a gas smell come and go?

Yes, it happens all the time. When plumbers work on gas piping systems, they shut the gas off before disconnecting any of the pipes, but when they do disconnect the pipes, residual gas in the pipes is released, leaving behind the classic odor for a few seconds. The odor dissipates quickly and the plumber gets to work.

Does a gas leak smell constantly?

Slow gas leaks may not produce enough natural gas smell to be detectable, and even large leaks may not be detected by people with a diminished sense of smell. For these reasons, it is recommended that homeowners use a natural gas detector to alert them to the presence of natural gas.

Can a gas leak smell be intermittent?

A possibility of being intermittent could be if there is a leak between the line going from the ignition assemble to the burner. Then it would only leak when the water heater was on.

What can smell like a gas leak but isn't?

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.

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What can be mistaken for a gas leak?

Although Alliant Energy adds a distinctive odor to natural gas as a safety precaution to assist in the detection of leaks, your sense of smell might not be enough to detect a leak. Strong smells in the area, like cooking or chemical odors, can mask the smell of natural gas.

Is it normal to smell a little bit of gas?

It's also possible for a faint mercaptan smell/odor to linger if the pilot light in appliances like hot water heaters or gas fireplaces goes out or when you light a stove. Therefore, a mild propane smell may not be a cause for alarm. Nevertheless, If you detect this unpleasant smell, you must take action immediately.

How long can a gas leak go unnoticed?

Gas leaks are subtle in smell but very obvious in bills. They can even go on for months undetected.

How much gas smell is normal?

The Short Answer Is: It is not normal to smell gas near your furnace. The presence of a gas odor can indicate a potentially dangerous gas leak, which should be taken seriously.

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.

Is a faint smell of gas normal?

Keep in mind that, if the smell is faint, this is not necessarily a cause for alarm — it's perfectly normal for a natural gas smell to linger if you're lighting your stove or when the pilot light for one of your appliances goes out.

Is a small gas leak an emergency?

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.

Does smelling gas always mean a leak?

In some instances, the smell of gas may be present naturally. However, leaks can occur, and we want to make sure they are resolved as quickly as possible. Natural gas is odorless, but an additive called mercaptan is included to alert people of leaks.

Is it safe to stay in a house that smells like gas?

Here's what you should DO if you smell gas: DO leave the home, building, or area of the suspected leak. Get to a safe area as quickly as possible. After leaving your home, DO call the 24-hour emergency number for Peoples at 1-800-400-4271, or call your local emergency response number.

Why can I randomly smell gas?

Phantosmia refers to detecting smells that aren't really there. It's a symptom of many common conditions, including allergies, colds and upper respiratory infections. It could also indicate a brain-related condition, including epilepsy, stroke or Alzheimer's disease.

What if I smell gas but no leak?

If your home smells like gas, but there's no apparent leak, here are steps you should follow: Ventilate the house by opening all windows and turning on ceiling fans. After this, if the smell is persistent, evacuate your home. Put out any materials that can create a flame or cause a spark, such as any open flames.

What smell can be mistaken for gas?

Hydrogen Sulfide

The gas has a strong scent of rotten eggs, which makes it distinct from other, similar gases. If you detect this rotten egg scent and you are using hydrogen sulfide at your facility, this could be evidence of a leak.

When should I be concerned about smelly gas?

Foul-smelling gas can occur for many reasons, but sometimes it can indicate serious issues. Talk to your doctor if you have consistently foul-smelling gas accompanied by the following symptoms: Bloody and inconsistent stool (poop) Change in frequency of bowel movements.

Can a minor gas leak make you sick?

Gas leaks cause a reduction in oxygen which can lead to certain physical symptoms. If you're experiencing natural gas poisoning you might experience: Ringing in your ears. A reduced appetite.

How can you tell if you have a small 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.

How long does it take for a gas leak to harm you?

Severe leaks can cause this problem in just five minutes. The EPA states that exposure to concentrations of nine ppm or more for eight hours is enough to produce harmful health effects for at-risk individuals. Exit the property and call 911 if you suspect your home has a gas leak.

Why does my house suddenly smell like a skunk?

A natural gas leak will usually smells like rotten eggs or a skunk-like odor. If something doesn't smell right, or if you hear a funny hissing noise, tell an adult right away. If you if think the smell is natural gas, get out of the house as fast as you can and find an adult.

Is it normal to smell a little natural gas?

Natural gas has no odor. Gas companies add a harmless chemical called mercaptan to give it its distinctive “rotten egg” smell. All natural gas and 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.

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.

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