Smell gas in the house? Do this now
Last reviewed · Not medical advice
Get everyone out, don't touch switches or anything that can spark, and call your gas utility or 911 from outside — propane homes call the supplier or 911. Don't try to find the leak yourself. Calling when you're not sure is the right call — the gas industry's own guidance is to always report a gas smell and not assume someone else will. Everything else on this page comes after that call.
Most likely causes
Ranked for this situation. Open any cause for checks and fixes.
- 1
Natural gas leak
most commonAct nowIn a home with gas service, a gas smell is treated as a leak until the utility says otherwise.
Points to this:- Strongest near the stove, furnace, water heater, dryer, or gas meter
- Hissing or whistling near a line or appliance
- Smell came on suddenly and doesn't fade with ventilation
Check it, fix it, who to call
Safe checks- Do not hunt for the leak. If the smell is strong or you're unsure, leave and call from outside.
- A faint smell right at the stove: check whether a burner knob was left on without lighting. If so, turn it off and air the room — and leave and call if the smell doesn't clear quickly.
Fix- The utility (natural gas) or supplier (propane) finds and isolates the leak.
- A licensed plumber or gas fitter repairs the line or appliance connection.
DIY stops here: There is no DIY step beyond leaving and calling. Don't use soapy-water tests indoors while the smell is present.
Who fixes it: Your gas utility's emergency line
More on this - 2
Propane leak
most commonAct nowIn propane homes. Propane settles low, so check basements and floor level from a distance — don't go looking.
Points to this:- Home or appliance runs on a propane tank
- Smell strongest low down or near the tank, regulator, or an appliance
Check it, fix it, who to call
Safe checks- Leave, then close the tank's main valve (clockwise) only if you can reach it safely.
- Call your propane supplier or 911 from a safe distance.
Fix- Your supplier or a qualified technician leak-tests and repairs the system before relighting.
DIY stops here: Beyond closing the tank valve on the way out, nothing — don't relight pilots yourself after a leak.
Who fixes it: Your propane supplier
More on this - 3
Gas smell drifting in from outside
commonSame dayStronger outside or near the meter; still the utility's job.
Points to this:- Smell is stronger outdoors or near the meter than inside
- Comes and goes with the wind, or started when nearby digging began
Check it, fix it, who to call
Safe checks- Note where outside it is strongest, then call the gas utility — outdoor leaks are their job too.
Fix- The utility locates and repairs outdoor and street leaks.
DIY stops here: Report it; don't dig, touch the meter, or probe around lines.
Who fixes it: Your gas utility's emergency line
More on this - 4
Dried-out drain trap
less commonSewer gas is the most common look-alike — but only once gas is ruled out.
Points to this:- Smell is near a guest bath, basement floor drain, unused shower, or utility sink
- Started after a trip, or in a room nobody uses
- Goes away after running water
Check it, fix it, who to call
Safe checks- Run water in every sink, tub, and shower for 30 seconds, and pour a bucket of water into floor drains.
- Flush toilets that rarely get used.
- Wait a few hours. If the smell is gone, it was a dry trap.
Fix- Run water in rarely used fixtures every couple of weeks.
- For floor drains that dry out constantly, a plumber can fit a trap primer or a trap-seal insert.
DIY stops here: If refilling the traps doesn't stop it within a day, the problem is past the trap — call a plumber.
Who fixes it: Plumber
More on this - 5
Water heater reaction (sulfur in hot water)
less commonA look-alike only if the smell is tied to hot water.
Points to this:- Only the hot water smells; cold water from the same faucet is fine
- Worse after the heater has sat unused, or after a vacation
Check it, fix it, who to call
Safe checks- Fill one glass with hot water and one with cold, step away from the sink, and smell each.
- Check whether the smell appears at every hot tap (water heater) or just one (that fixture's drain).
Fix- Flush the water heater.
- Have a plumber replace the magnesium anode with an aluminum-zinc or powered anode.
- Ask a plumber about sanitizing the tank.
DIY stops here: Anode replacement on a gas or electric heater is usually a plumber job — you're working with gas lines or 240V and a pressurized tank.
Who fixes it: Plumber
More on this
How we rank causes: by how often each one explains this smell in ordinary homes, according to plumbing, HVAC, electrical, and building-science guidance, adjusted for the context on this page. The labels are judgments, not measured statistics. Anything dangerous that can't be ruled out (gas, fire, electrical) is covered in the safety box at the top of the page, whatever its rank.
Which one is it?
| Situation | What to do |
|---|---|
| Strong smell anywhere inside | Leave, then call from outside |
| Hissing near a line, meter, or appliance | Leave, then call from outside |
| Smell outdoors near the meter or street | Move away and call the utility |
| Faint smell right at the stove, a burner knob left on | Knob off, open windows, leave the room — call if it doesn't clear quickly |
| Smell only when hot water runs, never near appliances | Probably the water heater — see the rotten-egg page |
| Utility came and found no leak | See the no-leak page |
Narrow it down
Answer in order. Stop at the first yes.
- 1Is the smell strong, or is there hissing, or does anyone feel unwell?Yes → Leave now and call from outside. Nothing else first.No → Keep going — but if in doubt, leave and call anyway.
- 2Is it faint and only at the stove, with a burner knob left on?Yes → Turn the knob off, open windows, and leave the room. If the smell doesn't clear quickly, follow the leave-and-call steps.No → Call the utility. A faint gas smell with no obvious reason still needs a check.
- 3Has the utility already checked and found no leak?Yes → Work through the look-alikes. Go there
Safe checks you can do yourself
In the order that finds the source fastest.
- 1
From outside: make the call
Call your gas utility's emergency number, or 911. On propane, call your supplier or 911. Tell them where you smelled it and whether you heard hissing.
- 2
Keep everyone out
Wait at a distance — not in the attached garage, and don't start a car in it. Don't go back in for belongings or pets.
- 3
After it's cleared: relight safely
If the gas was shut off, let the utility or a qualified technician restore it and relight pilots. Propane systems need a leak check before appliances go back into use.
- 4
Check your CO alarms
Carbon monoxide has no smell, so the gas smell tells you nothing about CO. Make sure alarms are on every level and outside sleeping areas.
What happens when the utility arrives
A technician uses a gas detector to check the air, the meter, and the line into the house, and usually the connections at your gas appliances. If they find a leak, they shut off the gas to the leaking part or the whole house and tell you what has to be repaired. Leaks on your side of the meter are typically repaired by a licensed plumber or gas fitter, at your cost. Follow their instructions about when it's safe to go back in.
Gas or not gas? Only after it's safe
Sewer gas, a smelly water heater, and some drain problems can smell almost exactly like the odorant added to gas. That's why location matters. A smell near a gas appliance, the meter, or a gas line is treated as gas. A smell that's only at a drain, or only from hot water, is more likely the plumbing. But you don't need to work that out before calling — a no-leak visit is a good result, not a wasted one.
When DIY stops
- There is no DIY for a suspected gas leak beyond leaving, closing a propane tank valve on the way out if it's safe, and calling.
- Don't use soapy water, matches, or a flashlight to hunt for leaks indoors.
- Don't relight pilots or restore gas yourself after a shut-off unless the utility tells you it's fine.
Who to call
- Your gas utility's emergency line
Natural gas: any time you smell it. Call from outside.
Checks for natural gas leaks. Call its emergency number, not the billing line.
- Your propane supplier
Propane: call your supplier from a safe distance.
Checks propane tanks, lines, and appliances for leaks.
- 911 / fire department
You can't reach the utility or supplier, or anyone is unwell.
Responds to smoke, fire, and gas emergencies.
- Plumber
After a leak is found on your side of the meter — a licensed plumber or gas fitter repairs it.
Drains, traps, toilets, vents, water heaters, and leaking supply lines.
Answer a few questions about where and when you smell it. You'll get the causes ranked for your situation.
Frequently asked questions
Should I open windows if I smell gas?
Don't stay behind to do it. The priority is getting out without causing a spark. Opening a door on your way out is fine. Hunting for windows to open is not.
Can I use my phone inside if I smell gas?
Industry safety guidance says to call from outside, away from the building, and not to use phones or anything electrical inside where gas may be present.
Is a small gas smell near the stove normal?
A brief whiff when a burner lights can happen. A smell that lingers, or appears with the burners off, is not normal — call the utility.
Does the gas company charge to check for a leak?
Policies vary by utility, so ask yours — but never let cost stop you from calling. Repairs to lines and appliances on your side of the meter are usually your responsibility.
What does propane smell like?
Like natural gas: rotten eggs, sulfur, or skunk. Propane is heavier than air, so it can collect near the floor and in basements.
Related smells
Sources
- Using Natural Gas Safely — American Gas Association
- Safety Guide for Propane Users — Propane Education & Research Council
- Pipeline Leak Recognition and What to Do — U.S. DOT PHMSA
- Carbon Monoxide Information Center — U.S. CPSC