Do You Smell Gas? How to Tell If It's a Natural Gas Leak and What to Do

If you smell a rotten-egg or sulfur odor in your home, treat it as a natural gas leak until someone with the right equipment proves otherwise. Do not wait to see if the smell goes away. Get out now, call 911 from outside, and let the professionals sort it out. The rest of this page explains what you are smelling, what to do step by step, and what mistakes can turn a minor leak into a catastrophe.

SAFETY ALERT — READ THIS FIRST

If you smell rotten eggs or sulfur inside your home right now:

Leave immediately. Do not flip switches, use your phone, or touch anything electrical before you go.

Get every person and every pet out of the building.

Once you are well away from the house, call 911 and your gas utility's emergency line.

Do not go back inside until the fire department or gas company tells you it is safe.

Is a gas smell dangerous?

Yes. Natural gas is highly flammable. At a concentration of about 5 to 15 percent in air, it can ignite from a spark as small as the one a light switch makes. An explosion or a fast-moving fire can follow within seconds. In addition to the fire risk, natural gas displaces oxygen in an enclosed space, which can cause asphyxiation at high concentrations.

Gas leaks are not common, but they do happen, and the consequences can be severe. The U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) tracks thousands of pipeline incidents every year across the country's gas distribution system. Taking a gas smell seriously every time — even if it turns out to be nothing — is the right call.

How to know it's natural gas

Natural gas in its raw form has no color and no smell. Because that makes it impossible to detect without instruments, federal law requires gas utilities to add an odorant before the gas reaches your home. Under 49 CFR 192.625, combustible gas in distribution lines must be odorized so that a person with a normal sense of smell can detect it at one-fifth of the lower explosive limit — well before it reaches a dangerous concentration.

The odorant is a compound called mercaptan (also written as methanethiol). It contains sulfur, which is why the smell is described as rotten eggs, sulfur, or a struck match. Even a tiny amount of it — less than one part per million — is enough for most people to notice.

Beyond smell, here are the other signs of a natural gas leak:

A hissing or blowing sound near a gas line, meter, or appliance. This means gas is escaping under pressure.
Dead or dying vegetation in an otherwise healthy patch of yard. An underground pipe leak can starve plant roots of oxygen, killing grass or shrubs in a ring or streak above the pipe.
Dirt, dust, or small debris blowing up from the ground near a buried line with no other explanation.
Bubbling in a puddle or wet area of your yard.
An unexplained jump in your gas bill without a change in your usage habits.

Important limitation: do not rely on smell alone. A condition called "odor fade" can reduce the concentration of mercaptan in the gas before it reaches your nose, especially in new steel pipes, where the odorant can be absorbed into the pipe walls. Some people also have a diminished sense of smell. A natural gas detector installed in the home gives you a reliable second line of defense.

If you are smelling something that seems more like sewage or rotten eggs coming from a drain rather than from a gas appliance or pipe, it may be a different problem entirely. Read our guide on a sewer or rotten-egg smell that turns out to be a plumbing or drain issue. And if the smell seems to come specifically from your stove or oven burners, see our related guide on a gas smell coming from your oven or stove.

What to do right now

Follow these steps in order. Speed matters, but staying calm will help you move faster.

1. Stop what you are doing and leave immediately. Do not pause to open windows, blow out candles, or gather belongings. Leave the door open behind you as you go — that is fine — but do not do anything that could create a spark. Walk, do not run, to avoid static buildup from clothing.

2. Get everyone out, including pets. Alert anyone else in the home as you move toward the exit. Do not go back in for people or animals unless you are sure you can get them out in seconds with no risk.

3. Do not touch any switches, buttons, or electrical devices before you leave. This includes light switches, appliance switches, the garage door opener button, doorbells, and your phone or tablet. Even plugging in or unplugging a device can create a small arc. Do not start your car if it is parked inside an attached garage.

4. Leave the home. Do not stop to find the source of the leak. It is not your job to locate or fix a gas leak. Leave that to trained technicians with the right detection equipment.

5. Once you are well away from the building — ideally at least one house-width away — call 911. Give the dispatcher your address and tell them you suspect a natural gas leak. Also call your gas utility's emergency line. Most utilities have a 24-hour emergency number printed on your bill. Both 911 and the gas company will respond, often at the same time.

6. Do not go back inside until authorities clear the building. Even if the smell seems to have faded when you step back toward the door, do not re-enter. A fading smell can mean the gas has accumulated to a dangerous level rather than dispersed.

What NOT to do

The following actions can turn a gas leak into an explosion or fire. Many of them feel instinctive in an emergency, which is why it helps to review them now, before you are in that situation.

Do not flip any light switch on or off. The small electrical arc inside the switch can ignite gas.
Do not turn any appliance on or off — stove, range hood, dishwasher, dryer, anything.
Do not use your cell phone, cordless phone, or landline inside the building. Wait until you are well away from the structure.
Do not press the garage door opener button — inside the garage or on the wall. The opener motor creates sparks.
Do not light a match, candle, or lighter for any reason.
Do not use a flashlight inside the building if you can avoid it. If you must see in the dark, leave quickly rather than turning one on.
Do not try to turn off the gas yourself at the meter unless the fire department or your utility has specifically trained you to do so and you have the right tool. Improperly shutting off a meter can itself create a spark.
Do not assume someone else will call it in. If you smell it and you leave, make the call yourself.

What causes gas leaks

Understanding how leaks happen can help you prevent them. The most common causes in a home include:

Aging or corroded pipes. Steel pipes can rust over decades, and older flexible connectors behind appliances can crack. Homes with original cast iron or galvanized steel gas lines are at higher risk.
Loose fittings and connections. A connection that was not tightened properly during installation, or one that has been bumped or stressed, can seep gas. This is especially common behind appliances that have been moved.
Appliance problems. A gas range, furnace, water heater, or dryer with a failing valve, a cracked burner, or a faulty pilot light assembly can leak.
Digging without calling 811. Excavation — whether by a contractor or a homeowner planting a tree — is one of the most common causes of gas line damage. Before any digging project, call 811 (the national "Call Before You Dig" number, required by federal law) or submit a request at call811.com. Your state utility-locating service will mark underground lines at no charge within a few business days. The American Gas Association (AGA) and PHMSA both emphasize that accidental excavation damage is a leading cause of unplanned gas outages and pipeline incidents.
Seismic activity or shifting soil. Ground movement can stress buried pipes and pull apart joints.
Earthquake or flood damage. After any significant natural event, have a licensed technician inspect your gas system before turning it back on.

When to call a pro

Call a licensed plumber or gas technician — not a handyman — any time you notice:

A persistent faint gas odor that comes and goes, even if it is subtle
An unexplained increase in your gas bill
A gas appliance that will not stay lit or has a yellow or orange flame instead of a steady blue one
Visible rust, corrosion, or physical damage on gas pipes or connectors
Hissing sounds near any gas line or appliance
Any time after you have had excavation work done near your home
After a flood, earthquake, or other event that could have shifted or damaged underground pipes

Do not attempt to repair a gas line yourself. Gas line work requires a licensed professional and, in most states, a permit and inspection. A botched DIY repair can create the very leak you are trying to fix.

How to prevent leaks (detectors and inspections)

Install a natural gas detector. A dedicated combustible-gas detector will alarm before gas reaches a concentration your nose can reliably catch. The National Fire Protection Association's new NFPA 715 standard provides installation requirements for residential fuel gas alarms. Look for a UL-listed unit and follow the manufacturer's instructions for placement — typically near floor level for natural gas, since it is lighter than air but can pool near appliances. Test it monthly and replace it per the manufacturer's schedule.

Install a carbon monoxide detector too. A gas leak can also lead to incomplete combustion, which produces carbon monoxide — an odorless, colorless gas that can be fatal. The NFPA recommends CO alarms on every level of the home and outside each sleeping area. Replace them every 5 to 7 years or as the manufacturer specifies.

Schedule annual appliance inspections. Have a licensed HVAC technician or plumber inspect your gas furnace, water heater, range, and dryer connections once a year. Many utilities offer free or low-cost appliance safety checks — check your utility's website.

Know where your gas meter is and how to shut it off. You will need a special wrench (or an adjustable wrench) to close the shutoff valve on the meter. Ask your utility about the correct procedure. In an emergency, only do this if the fire department or utility specifically directs you to.

Call 811 before any digging. Whether it is a fence post or a large landscaping project, call 811 at least two business days before you break ground. It is free and legally required.

FAQ

Q: What does natural gas smell like? A: Natural gas is odorized with mercaptan, a sulfur compound. Most people describe the smell as rotten eggs, sulfur, or a struck match. Even a faint trace of this smell near a gas appliance or pipe is worth taking seriously.

Q: Can a gas leak make you sick? A: In low concentrations, natural gas is not directly toxic, but it displaces oxygen. In an enclosed space with a significant leak, you may feel lightheaded, short of breath, or nauseous. A gas leak can also lead to carbon monoxide buildup from incomplete combustion, which is more immediately dangerous to health. If you feel suddenly sick and also notice a gas smell, leave immediately and get fresh air.

Q: I smelled gas for a moment and then it went away. Is it safe to stay? A: No. A smell that comes and goes can mean a slow, intermittent leak. It can also mean that gas has accumulated and the odorant is dispersing while the gas concentration is still rising. Leave and call 911 and your gas utility to have the space inspected before you return.

Q: Can I open a window to clear the gas before I call? A: Opening a window on your way out is fine, but do not stop to open multiple windows. The priority is getting yourself and others out of the building as quickly as possible without creating a spark. Do not turn on a ventilation fan — the motor can produce a spark.

Q: How long does it take for the gas company to respond? A: Gas utilities treat suspected leaks as emergencies and typically respond within minutes to an hour, depending on location. The fire department also responds to 911 gas-leak calls and will often arrive first. Do not go back inside until both 911 responders and the gas utility have inspected and cleared the building.

Get a licensed pro for a gas line inspection or repair

If you have noticed any warning signs — a faint gas smell, a high bill, an appliance acting up, or aging pipes — do not wait for a full emergency. A licensed plumber or gas technician can inspect your lines, test for leaks with specialized equipment, and make code-compliant repairs.

Use Local Service Group to find a vetted, licensed gas and plumbing pro near you and get a free quote. There is no obligation, and finding a problem early is far less expensive than dealing with one after it escalates.

Sources

U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) — 49 CFR Part 192, Pipeline Safety Regulations, Section 192.625 (Odorization of Gas): https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-D/part-192
American Gas Association (AGA) — "Using Natural Gas Safely": https://www.aga.org/natural-gas/safety/using-natural-gas-safely/
Fire Department, City of New York (FDNY) — "Natural Gas Safety" public fire safety education sheet: https://www.nyc.gov/assets/fdny/downloads/pdf/fire-safety-education/14_natural_gas_english.pdf
National Fire Protection Association (NFPA) — "Staying Safer from Natural Gas and Propane Leaks and Explosions" (NFPA 715): https://www.nfpa.org/news-blogs-and-articles/blogs/2025/02/13/residential-fuel-gas-alarms-and-nfpa-715
Nicor Gas (Southern Company Gas) — "Smell Gas? Act Fast!" Emergency Information page: https://www.nicorgas.com/safety/emergency-information.html
PHMSA — Final Rule, Gas Pipeline Leak Detection and Repair: https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-01/PHMSA%20Final%20Rule%20-%20Gas%20Pipeline%20Leak%20Detection%20and%20Repair%20-%20As%20submitted.pdf
Common Ground Alliance / Call 811 — Safe Digging Program, AGA co-founder: https://call811.com/

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Home systems involving gas, electricity, water, refrigerant, fire, or structural components can be hazardous, and requirements vary by local code and jurisdiction. Any inspection, diagnosis, repair, installation, or other action referenced on this page should be performed by a licensed professional. You should not rely on this content to perform such work yourself. To the fullest extent permitted by law, [Company Name] and its owners, employees, and contributors assume no responsibility or liability for any injury, death, property damage, or other loss arising out of or in connection with the use of, or reliance on, this information.

If you smell gas or suspect a carbon monoxide leak, leave the area immediately and call 911 or your gas utility from a safe location.