A dusty, hot smell the first time the heat runs in the fall is usually settled dust warming on furnace components after a summer of sitting idle, and it normally fades while the system runs. Other smells are not dust, and each one has a different response. Carbon monoxide is odorless and colorless, so no smell check of any kind tells you whether it is present.
If you see smoke or flame
Get everyone out and call 911. Nothing below applies until that is done.
If you smell gas
Leave first. Federal pipeline safety guidance is to leave the area on foot immediately and not to try to find the source. Do not use a phone inside the building, do not touch light switches or unplug anything, and do not start a vehicle in an attached garage, because any of those can be an ignition source. Once you are well away from the building, call 911, then your gas utility’s emergency line. Do not go back in to check whether the smell has cleared.
If a carbon monoxide alarm sounds
Get everyone outside into fresh air and call 911. Do not go back in to ventilate or to investigate. The CDC lists the symptoms of carbon monoxide poisoning as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. If anyone develops these symptoms and carbon monoxide exposure is possible, get everyone outside and call 911, even if no alarm has sounded. Do not wait to see whether symptoms improve outdoors.
If you smell hot plastic or something electrical
Switch the system off at the thermostat and leave it off. That smell can mean an electrical part or wiring is overheating, which can create a fire hazard. Do not run the system again until it has been checked, and if smoke or flame appears, treat it as the first case above.
What dust burn-off looks like
Dusty rather than sharp, present on the first run of the season, and fading while the system keeps running. Changing the filter beforehand helps, and opening a window while it clears is reasonable if the smell bothers you. A smell that persists instead of fading, gets stronger, or returns on later cycles is not something to dismiss as normal dust burn-off. At that point stop treating it as dust and have the system checked.
Run the heat before the first cold night
Run the system once on a mild day before you need it, with a window open: settled dust may burn off, and if something seems wrong you can book a check before you depend on the heat. A test run will not reveal every fault. That test tells you nothing about carbon monoxide. The CDC’s guidance on that is to have heating systems serviced by a qualified technician every year and to put battery-operated or battery-backup carbon monoxide detectors in the home, installed near every sleeping area.
Heating repair in Arlington: what to do next
Book a heating check in Arlington, or use the contact details on the Arlington location page. Furnace repair and installation are covered on the furnaces page. When you book, it is fair to ask what the visit includes and whether it covers an inspection of the heat exchanger.
Common questions
The dusty smell went away after ten minutes. Is that fine?
A dusty smell that fades on the first heating run can be consistent with dust burn-off, but fading alone does not confirm that the system is safe. A gas, hot-plastic or electrical smell needs the response described above, even if it fades. A fading smell cannot rule out carbon monoxide; follow the carbon monoxide alarm and symptom guidance above. A dusty smell that returns on later cycles needs a check.
I have a heat pump. Does any of this apply?
The dust burn-off does, if it has electric backup heat: the strips burn off settled dust the same way. A heat pump that burns no fuel is not a gas appliance. That does not make a gas smell in the house any less serious, because a water heater, a range, a fireplace or the supply itself can leak regardless of what heats your home. A gas smell gets the same response either way.