Safety first: official instruction
If you smell gas, leave now and call from outside
From the U.S. DOT Pipeline and Hazardous Materials Safety Administration (PHMSA), quoted:
- “Leave the area by foot immediately. Do not try to locate the source of the odor or leak.”
- “Call 911 from a safe location; then, notify the pipeline company and or your local emergency response number if known.”
- “DO NOT cause any open flame or other potential source of ignition such as an electrical switch, vehicle ignition, light a match, etc.”
- “DO NOT use telephone or cell phone.”
For a home, the “pipeline company” is your gas utility (or your propane supplier). Trane’s furnace guidance says the same thing in household terms: do not light any appliance, do not touch any electrical switch or garage door opener, leave with your family and pets, and call the gas company once you are outside and away from the house[2].
Source: U.S. DOT PHMSA: Pipeline leak recognition and what to do.
Symptom guide
Furnace smells like gas: what to do and what happens next
By the HeatAndAirCost editors · Last updated October 5, 2026 · How we research prices
What people commonly report
The reports vary: a gas smell at the furnace when it starts, a smell in the basement or utility closet that comes and goes, or a faint odor near the registers. Some people also hear a hiss near the furnace. None of the sources on this page sets a “too faint to matter” level. Trane’s instruction for a gas or rotten-egg smell anywhere in the home is to leave immediately and call the gas company from outside[3].
What official and manufacturer sources say
- Why you can smell it. PHMSA explains that gas distribution systems are odorized with mercaptan, “a harmless non-toxic chemical that is added to make it easier to detect a gas leak due to its skunk like odor”[1]. Trane notes that natural gas itself is odorless[3].
- The furnace may not be the source. Trane lists the gas furnace, gas water heater, gas fireplace and gas stove as places a household gas leak can be traced to[3]. That is one more reason not to search for it yourself.
- Sound can come with it. PHMSA says a leak can sound like anything from “a quiet hissing to a loud roar” depending on its size[1]. Trane says a hissing sound near a furnace may mean a gas leak[3].
- Gas connections are a maintenance item. ENERGY STAR’s checklist for a heating tune-up includes checking all gas connections and gas pressure, and states that improperly operating gas connections are a fire hazard[4].
What happens after you call
- The utility or fire department responds. Trane describes the sequence: they find the source, shut off the gas, air out the house, report what they found, and tell you when it is safe to go back in[2].
- Repairs inside the home are on the owner. Trane says the homeowner is responsible for repairs to any gas line or valve inside the home, and that an HVAC contractor or a plumber can do that work[2].
- Do not relight anything yourself while the smell is present. “Do not try to light any appliance (furnace or gas stove)” is the first line of Trane’s list[2].
- Keep up the yearly inspection. The U.S. Fire Administration advises having heating equipment cleaned and inspected by a professional every year[6].
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After the house has been cleared
PHMSA mentions home gas detectors as part of good safety habits, and CPSC recommends CO alarms on every level of the home. These add a warning. A detector is never a reason to stay in a house that smells of gas.
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When to stop and call
- Any gas or rotten-egg smell: leave and call from outside. See also why gas smells like rotten eggs.
- Hissing near the furnace, gas line or meter: treat it as a possible leak, per Trane and PHMSA[1].
- A CO alarm sounding: that is a separate emergency with its own steps. See CO detector going off.
Related guides
What the repair can cost
Related problems
Sources
- U.S. DOT PHMSA: Pipeline leak recognition and what to do
- Trane: Why does my furnace smell like burning?
- Trane: HVAC smells and sounds, explained
- ENERGY STAR (EPA/DOE): Heating and cooling maintenance checklist
- U.S. Consumer Product Safety Commission: Carbon Monoxide Fact Sheet
- U.S. Fire Administration: Heating fire safety
This page is general information collected from the official and manufacturer sources listed above. It is not an inspection or a diagnosis of your system, and only a qualified technician who sees the equipment can tell you what is wrong. For a gas smell, follow PHMSA’s instruction and your gas utility’s emergency line, not this page. HeatAndAirCost is not affiliated with PHMSA, the U.S. Consumer Product Safety Commission, ENERGY STAR, the U.S. Fire Administration, Trane, any gas utility. Found an error? hello@heatandaircost.com.
Getting local help
Finding a qualified technician
We do not inspect systems, rate contractors, or recommend any particular company. Whoever you call, ask for the license number and look it up on your state or county licensing board’s public site before work starts. Refrigerant work also requires an EPA Section 608 certified technician. Our contractor hiring checklist covers licenses, insurance, written quotes and red flags.
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People also ask
Furnace smells like gas: FAQs
What should I do if my furnace smells like gas?
Federal pipeline-safety guidance from PHMSA says to leave the area on foot immediately without looking for the source, then call 911 from a safe location and notify the gas company. Do not switch lights or appliances on or off, start a car, light anything, or use a phone while you are still inside.
Should I turn the furnace off before I leave?
PHMSA's list begins with turning off gas appliances, and it also says to avoid any ignition source, including electrical switches. Trane's homeowner list says not to touch any electrical switch and to leave with your family and pets. Neither source tells you to stay inside to work on the furnace or hunt for the leak. Getting out and calling from outside is the step every source shares.
Who fixes a gas leak at the furnace?
According to Trane, the gas company or fire department finds the source, shuts off the gas, airs out the house, and tells you when it is safe to go back in. Repairs to gas lines or valves inside the home are the homeowner's responsibility, and Trane says an HVAC contractor or a plumber can handle them.
Does a gas furnace need a carbon monoxide alarm?
CPSC recommends CO alarms on every level of the home and outside sleeping areas, and lists malfunctioning furnaces among the products that produce CO. A gas leak and carbon monoxide are different hazards: a CO alarm does not detect a gas leak, and gas odorant does not warn you about CO.