If your furnace smells while running, it’s attempting 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:
- 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 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 up when you turn on the heat, causing 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 problem. This smell of burning can be created by melting plastic wire casing, which is a safety hazard. If you’re experiencing 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 overheated or the heat exchanger is cracked. The heat exchanger safely exhausts carbon monoxide that’s naturally created during the combustion process.
If it cracks, carbon monoxide can seep into your house. This colorless gas is fatal in large doses. So, it’s important to have an HVAC professional do annual furnace maintenance and have working 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, such as formaldehyde
- Water near your furnace, as long as the condensate drain isn’t blocked
- Flu-like symptoms
3. Gas Smell from Furnace
It’s normal for your heating system to give off a small amount of gas when it starts up, so you might get a gas smell from your furnace. But it’s not typical to be smelling natural gas or rotten eggs throughout your home on a regular basis.
Cause: Gas Leak
If your furnace smells like gas continuously, turn it off. If you know where your main gas supply valve is, shut that off too. Then call the gas company and us for assistance.
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 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 issue, 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 a while.
Cause: Dirty Ductwork
Your furnace works with air ducts to distribute warm air throughout your house. Mold can grow in the ductwork as time goes on, especially if you live in a humid climate. You can eliminate the mold by having an HVAC technician do air duct cleaning.
Depend on Us with Your Furnace Repair Needs
Trying to fix your heating and cooling system on your own is difficult. Your comfort is our top priority at Contra Costa Heating & AC, so our professionals are here to help you when you need us. When you need furnace repair in that you can trust, contact us at .