Smell Gas in Your House? What to Do Right Now, and What Comes Next

Natural gas and propane have no smell of their own; suppliers add an odorant, mercaptan, so a leak smells like rotten eggs or sulfur. NW Natural, a gas utility, says leaks most often come from faulty appliances or someone accidentally hitting a line. Treat the smell as a leak until the utility checks: Washington Gas notes that not every suspected odor is a leak, but "this can only be determined by qualified personnel."

Other smells can pass for gas: a sewer smell from a drain (sewer smell in the house), a sulfur smell only from the hot water (rotten-egg hot water), and a dusty smell when the heat first comes on (furnace smells like burning). For a sounding CO alarm, see CO alarm going off. If you aren't sure it isn't gas, treat it as gas.

What to Do Right Now

1. Get everyone out. The American Gas Association (AGA) says to leave immediately and take others with you. Nicor Gas, an Illinois utility, says never to try to find the leak yourself, and NW Natural says to leave "no matter what," even if the smell seems mild.
2. Touch nothing that can spark on the way out. The list is under What Not to Do.
3. Leave the door open behind you, as CPS Energy, a Texas utility, and Washington Gas advise. Don't stop to open windows (see the FAQ).
4. Get well away, then call. DTE Energy says to go outside to where you can no longer smell gas, PG&E says upwind, and PSE&G says at least 350 feet away. Then call 911 and the gas utility. Don't assume a neighbor called; the AGA says always report it.
5. Stay out until you're told it's safe. Nicor and DTE say not to go back in until the gas company or emergency responders say so. The National Fire Protection Association (NFPA) says your gas provider must check the whole system before you use any gas appliance.

Smell gas outdoors? NW Natural says to leave the entire area.

What Not to Do

Nicor warns that a spark could ignite the gas, causing a fire or explosion.

• No flames. No lighters, matches, or cigarettes (Nicor, NW Natural).
• No switches, doorbells, or garage door openers. Nicor's list adds radios and TVs, CPS Energy adds appliances, and National Grid adds thermostats.
• No phones or flashlights inside. NW Natural includes "any mobile device that has a battery." Nicor says to wait until you're a safe distance away to use a cell phone.
• Don't start the car. Peoples, a Pennsylvania utility, says not to start a car or operate an automatic garage door near a leak, so a car in an attached garage stays put.
• Don't touch inside valves or try a repair. Peoples says not to operate any valves, and PSE&G says not to try to control or repair the leak.
• If the gas catches fire, let it burn. NW Natural says not to try to put it out. Get everyone out and call 911 from outside.
• Don't pull a gas alarm's battery to silence it, Nicor adds; the spark could cause an explosion.

Should You Shut Off the Gas at the Meter?

Utilities differ, so follow yours. PG&E says not to shut off your gas unless you smell gas, hear it escaping, see a broken line, or suspect a leak, and SoCalGas says to do it then "ONLY if it's safe to do so." Peoples says not to operate any valves, and NW Natural says leaving should be the priority. Getting out comes first: never stay inside, or go back in, to reach a valve. Our emergency shutoffs guide shows where the meter valve is and how to learn the rule ahead of time.

Once it's off, leave it off. PG&E, SoCalGas, and NW Natural all say not to turn the meter back on yourself.

On propane, once everyone is out, AmeriGas and the Pennsylvania Propane Gas Association say to turn off the main supply valve on the tank, turning it to the right (clockwise), if it's safe to do so.

Why Gas Smells Like Rotten Eggs

Utilities add mercaptan to colorless, odorless natural gas, and Nicor and Con Edison compare its smell to rotten eggs. Atmos Energy notes that regulations require gas to be "readily detectable by a person with a normal sense of smell." The Pennsylvania Propane Gas Association likens propane's added odor to rotten eggs, a skunk's spray, or a dead animal.

Why You Might Not Smell It

• Your nose gets used to it. The NFPA says olfactory fatigue sets in after a minute or two of the same odor.
• Your sense of smell is weaker. Atmos lists colds, sinus conditions, allergies, and loss of smell, and says tobacco, alcohol, or medications can dull it. The propane association adds age, and notes the odor may not wake a sleeper.
• Other smells mask it. DTE names candles and air fresheners.
• The odorant fades. Con Edison says it can fade in new piping, with rust or moisture in a pipe, with little or no gas flow, and when gas from an underground leak passes through soil. The propane association says air, water, or rust in a propane tank can weaken it, and running out lets air and moisture in. NIOSH, the federal workplace-safety institute, found odor fade was a key factor in a 2019 propane explosion that killed a firefighter.

So don't wait for a strong smell. Con Edison says to call even if you suspect a leak but can't smell it.

Other Signs of a Gas Leak

• Sounds: hissing, whistling, or roaring from a gas appliance or from underground (PG&E).
• Outdoors, over a buried line: dirt blowing from a hole, continuous bubbling in wet or flooded areas, and dead or discolored plants in an otherwise green area (DTE, Nicor). DTE adds frozen ground in summer or melted snow in winter.
• At the appliances: National Grid treats gas to an appliance that won't shut off, or abnormally high or low flames at all your gas appliances, as an emergency.

Indiana's utility regulators say you may feel light-headed or get a headache as leaking gas displaces the oxygen in a room. Odorless carbon monoxide causes headaches, dizziness, and nausea too (NFPA). If anyone has a headache, dizziness, or nausea, or a CO alarm sounds, get everyone outside to fresh air and call 911 from there.

Is It Gas or Something Else?

If you aren't sure, it's gas. Don't go back in to sniff drains or run taps to compare. For a smell you've already placed:

• Sewer gas. Wisconsin's health department says sewer gas, which contains rotten-egg-smelling hydrogen sulfide, gets in through floor drains, roof vents, and foundation cracks. A smell at a drain, away from gas appliances, the meter, and gas lines, belongs in our sewer smell guide.
• Rotten-egg hot water. A.O. Smith traces it to bacteria making hydrogen sulfide "you smell in the water." If it comes only with water from the hot tap, see the hot water guide. Treat a smell in the air around a gas water heater as gas.
• Dust burning off. Carrier says dust on the burner and heat exchanger burns off at the first heat-up, usually for about 30 minutes to a few hours. That's a burning smell; Carrier rates rotten eggs or sulfur an emergency. See furnace smells like burning.
• Skunk, dead animal, or burnt match. Don't dismiss these. The propane association compares propane to the first two, and DTE says natural gas can smell like a burnt match.

After the Gas Company Comes

Washington Gas says its technicians check with gas detection equipment and stay until the area is safe, and Atmos Energy and UGI say they investigate at no cost. Then it depends on where the leak is:

• The utility's side. UGI and CenterPoint Energy say the utility maintains everything up to and including the meter. Washington Gas says it permanently repairs all leaks on its system.
• Your side. Piping beyond the meter, into the house and to each appliance, is yours, UGI and CenterPoint say, including buried lines to a grill or pool heater. UGI says only qualified plumbing and heating contractors should inspect or repair it.
• A red tag. Peoples puts a red tag, an "Appliance or Piping Shut Off Notice," on an appliance or pipe with a dangerous condition. A qualified person, such as a professional natural gas plumber, must fix it before gas is restored, and you shouldn't use it until then.
• Who repairs appliances. Indiana's regulators say gas furnace, water heater, stove, fireplace, or dryer work belongs to "a licensed plumber or HVAC technician for instance." On propane, Connecticut's regulators say gas line repairs go to a licensed plumber where required, or your propane company.

Turning the Gas Back On and Relighting Pilots

SoCalGas says to call it to turn the meter back on and relight the pilots, and Washington Gas says its personnel or contractors relight appliances after restoring service. For a pilot that goes out later, PG&E says to follow the manufacturer's instructions, often inside the burner compartment door, wait five minutes for gas to disperse, and call a qualified professional if you can't relight it. The propane association strongly recommends a qualified technician light any propane pilot that has gone out.

Prevent It

Add a Gas Alarm to Your CO Alarms

The NFPA says gas alarms and CO alarms detect two different hazards, and a home with a fuel-burning appliance needs both. Its NFPA 715 standard doesn't require gas alarms, but it places them near fuel-burning appliances, in basements and attached garages where gas comes in, and outside sleeping rooms. Con Edison says to look for UL 1484 certification, an alarm point at or below 10% of the lower explosive level, and a lifetime battery, and to mount a natural gas detector within 12 inches of the ceiling in the room with the gas pipe or appliance. Propane is heavier than air and collects in basements, crawl spaces, and along floors (propane association), so place a propane alarm by its maker's instructions.

Atmos says an alarm is no substitute for your senses, and the Northeast Gas Association says to leave if you smell gas even when the alarm is quiet. Keep a UL-listed CO alarm on each level, as the propane association recommends; see our smoke and CO alarm guide.

• Yearly inspection. The Northeast Gas Association says to have fuel-burning heating equipment inspected by a licensed professional every year before cold weather. The fall checklist schedules it.
• Moves and connectors. Con Edison says to call a professional to move or replace a gas appliance. The propane association says to have connectors on appliances over 20 years old inspected, and not to move an appliance yourself to check one.
• Call 811 before you dig. Washington Gas names digging damage as a leading cause of gas leak emergencies. The AGA says to call 811 or use call811.com a few business days before any digging, including planting trees, and to wait until all lines are marked. CenterPoint notes utility locators don't mark customer-owned gas lines; a licensed plumbing contractor can.

Frequently Asked Questions

Should I open the windows if I smell gas?

Not if it keeps you inside. Washington Gas says to leave doors and windows open to ventilate "if possible," but Peoples says opening windows could make the area more unsafe. Leave the door open as you go, and get out.

I have propane. Who do I call?

Your propane company and 911, from a safe distance. AmeriGas says that if you can't reach your supplier, call 911 or the local fire department.

Will a carbon monoxide alarm detect a gas leak?

Usually not. Con Edison says most CO detectors don't detect combustible gases. Combination units exist, so check the label.

Is it dangerous to breathe natural gas?

Nicor says natural gas is non-toxic, but it displaces oxygen and in severe cases may lead to asphyxiation. It can also explode: Indiana's regulators say a mix of 5 to 15 percent gas in air is enough.

The Bottom Line

Rotten eggs, hissing, or any doubt: leave the house without switching anything on or off or using a phone inside, and call 911 and the gas utility once you're a safe distance away. Leave the door open, don't start the car, and stay out until the utility or fire department says it's safe. The utility handles its side and turns the meter back on; a licensed plumber or HVAC technician fixes your piping and appliances. Then add a gas alarm, keep CO alarms on every level, book a yearly inspection, and call 811 before you dig.

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