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Universal Air Systems

Troubleshooting

Strange Smell From Furnace

Quick answer

Burning-dust smell on first run of the season is normal. Sulphur or rotten egg = gas leak, get out and call the gas company. Burning plastic = call us.

Common causes

  • Burning dust (first run)

    easy

    Dust burning off the heat exchanger. Lasts 10 minutes, harmless. Open windows.

  • Burning plastic

    urgent

    An electrical component overheating. Shut off the furnace and call us — fire risk.

  • Sulphur / rotten eggs

    urgent

    Gas. Mercaptan additive smell. Get out. Call the gas company from outside.

  • Musty / mildew

    moderate

    Moisture in the ductwork or a clogged condensate drain. Clean drain, consider duct cleaning.

  • Smoky

    urgent

    Cracked heat exchanger venting combustion into the supply air. Stop using.

DIY first

  • 1 Identify the smell — burning, sulphur, musty, smoky.
  • 2 If gas: leave the house immediately. Don't use phone or light switch indoors.
  • 3 If burning plastic or smoky: turn off the furnace at the wall switch and call us.

Call us if:

  • Any smell other than first-of-season dust burn-off

Related service

Furnace Repair

Other symptoms in this category

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Diagnosis pointing somewhere serious? Call now.

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Mississauga, ON · Greater Toronto Area and up to 2 hours out — London, Kitchener, Barrie, Kingston, Niagara.

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