Why does my furnace smell like burning?
A dusty, slightly scorched smell on the first run of the season is normal — it's dust burning off the heat exchanger and clears within an hour. An electrical, plastic or persistent burning smell is not normal: shut the furnace off at the thermostat and call. If you smell gas or rotten eggs, leave the building and call 911 or your gas utility from outside.
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What you can safely check
- Is this the first burn of the season?
- Dust burning off smells scorched but clears within an hour or so. If it persists past that, treat it as a fault.
- Check the filter
- An overdue filter can scorch against a hot surface. Replace it and see whether the smell goes.
- Test your CO alarm
- Every home with gas appliances needs a working carbon monoxide alarm. If you don't have one, that's tonight's errand, not next month's.
What’s probably going on
- Electrical or plastic smell
- Overheating wiring, a failing motor or a melting component. Shut it down.
- Cracked heat exchanger
- The serious one. It can let combustion gases including carbon monoxide into your air. It cannot be diagnosed by smell alone and needs an inspection.
- Gas smell
- Never troubleshoot this. Out of the building first, call from outside.
Stop here and call
If you smell gas or rotten eggs, hear hissing, or your CO alarm sounds: leave the building first, then call 911 or your gas utility from outside. Do not flip switches or troubleshoot.
What we do about it
We inspect the heat exchanger, test combustion, and check for CO at the registers. If it's unsafe we red-tag it and tell you straight.
Still stuck?
Tell us what the system is doing and we’ll tell you what it takes to fix — free quotes, no obligation, and a straight answer about whether it’s worth repairing.