If your furnace smells while heating, it’s trying to tell you something’s up. We’ve put together a list of the top six furnace smells so you can know what causes them and how to fix them. These include:

  1. Burning smell from furnace
  2. Furnace smells like burning plastic
  3. Gas smell from furnace
  4. Furnace smells like sewer
  5. Furnace smells musty

1. The Furnace Smells Like It’s Burning

Cause: Dusty Furnace

If your furnace smells like burning, it’s probably occurring when you turn on your furnace for the first time in the fall. Like anything else in your house, your furnace gets dusty over time. This dust burns off when you turn on the heat, causing the burning dust smell from your furnace.

2. The Furnace Smells Like Plastic Is Burning

Cause: Electrical Problem

If your furnace smells like burning plastic or burning rubber, it might have an electrical problem. This smell of burning can be created by melting plastic wire casing, which is a safety issue. If you’re noticing a melted plastic smell, turn off your heating system right away and call us at 928-263-8570 for furnace repair.

Cause: Overheated Motor or Cracked Furnace Exchanger

An electrical burning smell could also mean your furnace motor is too hot or the heat exchanger is cracked. The heat exchanger safely exhausts carbon monoxide that’s naturally produced during the combustion process.

If it cracks, carbon monoxide can seep into your home. This invisible gas is fatal in large doses. So, it’s important to have an HVAC professional do routine furnace maintenance and have functional carbon monoxide detectors.

Other signs of a cracked heat exchanger include:

  • Soot on or inside the furnace
  • Yellow burner flame, instead of blue
  • Chemical smell from furnace, like formaldehyde
  • Water near your furnace, as long as the condensate drain isn’t plugged
  • Flu-like symptoms

3. A Gas Smell Is Coming From the Furnace

It’s normal for your heating system to let off a small amount of gas when it starts up, so you might notice a gas smell from your furnace. But it’s not normal to be smelling natural gas or rotten eggs throughout your home on a daily basis.

Cause: Gas Leak

If your furnace smells like gas frequently, turn it off. If you know where your main gas supply valve is, turn that off too. Then call the gas company and us for help.

4. The Furnace Smells Like Sewage

If your furnace smells like sewer, or rotten eggs, you’ll want to ensure you aren’t dealing with a gas leak. If you don’t, the issue could be with your sewer lines and not your furnace. This is especially true if it’s been very dry lately.

Cause: Dry Sewer Trap or Sewer Leak

If you think your sewer trap is dry, you can try putting some water down the floor drain in your basement. If that doesn’t solve the problem, you might have a sewer leak, so you’ll want to contact a company that does sewer line repair.

5. Furnace Smells Musty

If your furnace smells musty, mold and mildew have likely been growing in it for some time.

Cause: Dirty Ductwork

Your furnace uses air ducts to send warm air across your home. Mold can grow in the ductwork over time, particularly if you live in a humid climate. You can eliminate the mold by having an HVAC technician do air duct cleaning.

Depend on Us for Your Furnace Repair Needs

Troubleshooting your heating and cooling system by yourself is hard. Your comfort is our top priority at North Mechanical Heating and Cooling, so our professionals are here to help you when you need us. When you need furnace repair in Payson that you can trust, call us at 928-263-8570.