First: if you smell gas or see smoke
Natural gas has an added odor that smells like rotten eggs or sulfur. If you smell it, leave the house now. Don't flip switches or use your phone inside. Call your gas utility's emergency line or 911 from outside.
If you see smoke or flames, get everyone out and call 911. Once it's safe, call us so we can find the cause.
Normal: dust burning off
Over the summer, dust settles on the burners, heat exchanger and ducts. The first few times the furnace runs in the fall, that dust burns off and you smell it through the vents. It usually fades within the first hour or so of running. Opening a window for a bit helps. If the smell is still strong after the furnace has run for several hours, or comes back every time it starts, have it checked.
Smells that mean trouble
- Hot plastic, rubber or an electrical smell. It can mean an overheating motor, wiring or another electrical part. Turn the furnace off at the thermostat and call.
- A smell that gets stronger instead of fading. Something is overheating. Turn it off and call.
- Burning with the furnace starting and stopping. A clogged filter can make a furnace overheat. Replace the filter. If the smell and the cycling continue, call.
- Something stored too close. Boxes, laundry or cleaning supplies against the furnace, or a toy that fell into a floor vent, can scorch. Keep the area around the furnace clear.
- Smoky or exhaust-like smell. It can point to a venting or combustion problem. Turn it off, make sure your carbon monoxide alarms are working, and call. See Carbon monoxide and your furnace.
Musty smells
A musty or damp smell isn't burning, but it's common in fall too. It often comes from a humid crawlspace or basement, a wet drain pan or water sitting near the system. It's worth finding, because standing water can lead to mold and rust. See Furnace leaking water.
Prevent it next year
Run the heat for 15 to 20 minutes on a cool evening in early fall, before you really need it, so the dust burns off on your schedule. Change the filter at the start of the season, and keep the area around the furnace clear. A fall tune-up includes cleaning and safety checks. Our Comfort Club is $180 a year and covers a cooling tune-up in spring and a heating tune-up in fall, plus 20% off repairs and priority scheduling.
How HVAC Doctor can help
Call or text (859) 684-3259. One of the owners, Ahmad or Ammar, answers 24/7, and nights, weekends and holidays cost the same as a weekday. Mention our online special and the diagnostic is $39 (regularly $79), credited to the repair if you go ahead, and you get a firm price before any work starts. Most Lexington calls are same-day.
Common questions
How long should the burning smell last when I first turn on the heat?
Dust burn-off usually fades within the first hour or so of running. If the smell is still strong after several hours, or comes back every time the furnace starts, turn it off and have it checked.
Is a burning smell from my furnace dangerous?
The dusty smell on the first cold day usually isn't. An electrical or hot-plastic smell, a smell that gets stronger, smoke or anything that smells like gas is. For gas or smoke, leave the house and call your gas utility or 911 from outside. For an electrical smell, turn the furnace off at the thermostat and call.
Why does my furnace smell like burning plastic?
It can mean an overheating blower or inducer motor, a wiring problem, or something plastic touching a hot part or sitting in a vent. Turn the furnace off at the thermostat and call so the cause can be found before it runs again.
What does a gas leak smell like?
Utilities add an odorant to natural gas so it smells like rotten eggs or sulfur. If you smell it, leave the house, don't use switches or your phone inside, and call your gas utility's emergency line or 911 from outside.
Do you charge more for a call on the first cold weekend?
No. We're open 24/7 and nights, weekends and holidays cost the same as a weekday. Mention our online special and the diagnostic is $39 (regularly $79), credited to the repair if you go ahead.