If your furnace smells while heating, it’s attempting to tell you something’s wrong. 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:
- Burning smell from furnace
- Furnace smells like burning plastic
- Gas smell from furnace
- Furnace smells like sewer
- Furnace smells musty
1. Burning Smell from Furnace
Cause: Dusty Furnace
If your furnace smells like burning, it’s likely happening 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 up when you turn on the heat, resulting in the burning dust smell from your furnace.
2. Furnace Smells Like Burning Plastic
Cause: Electrical Problem
If your furnace smells like burning plastic or burning rubber, it might have an electrical issue. This smell of burning can be created by melting plastic wire casing, which is a safety hazard. If you’re noticing a melted plastic smell, turn off your heating system right away and call us at 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 gets rid of carbon monoxide that’s naturally produced during the combustion process.
If it cracks, carbon monoxide can leak into your home. This invisible gas is fatal in large doses. So, it’s important to have an HVAC professional do annual furnace maintenance and have functional carbon monoxide detectors.
Other symptoms of a cracked heat exchanger include:
- Soot on or inside the furnace
- Yellow burner flame, instead of blue
- Chemical smell from furnace, such as formaldehyde
- Water near your furnace, as long as the condensate drain isn’t plugged
- Flu-like symptoms
3. Gas Smell from Furnace
It’s normal for your heating system to let off a little bit 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 continuously, shut it down. If you know where your main gas supply valve is, turn that off too. Then call the gas company and us for help.
4. Furnace Smells Like Sewer
If your furnace smells like sewer, or rotten eggs, you’ll want to make sure you aren’t dealing with a gas leak. If you don’t, the problem could be with your sewer lines and not your furnace. This is especially true if it’s been extremely dry lately.
Cause: Dry Sewer Trap or Sewer Leak
If you suspect your sewer trap is dry, you can try putting some water down the floor drain in your basement. If that doesn’t solve the issue, you might have a sewer leak, so you’ll want to call 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 distribute warm air throughout your house. Mold can grow in the ductwork as time goes on, particularly if you live in a humid climate. You can eliminate the mold by having an HVAC technician do air duct cleaning.
Trust Us with Your Furnace Repair Needs
Troubleshooting your heating and cooling system by yourself is difficult. Your comfort is our top priority at Kohles & Bach Heating & Cooling, so our professionals are here to help you when you need us. When you need furnace repair in that you can trust, call us at .