List of Forced Air Gas Furnace Odors

Dust

• A dusty smell from your forced air gas furnace isn’t a big problem. Most likely, the combustion chamber is burning dust. This smell is common the first time you turn your furnace on for the season, and it usually doesn’t last more than an hour. You can cut down on the smell by dusting your furnace and changing the air filter before you turn on the furnace.

Electrical/Burning

• Loose electrical connections and overheating parts can cause electrical smells when wires, plastic relays and insulation becomes hot. Burning odors are worse than electrical odors and may be accompanied by smoke. Burning odors can be caused by wire or furnace parts burning up, or by plastic melting when it gets on the heat exchanger. If the odor reminds you of a burning clothes iron, it might indicate that the furnace is burning too hot because of a dirty filter. Change the filter and, if the smell continues, turn the furnace off and call your service technician. Your ducts may need to be cleaned. Smoky smells may mean that your burners need cleaning, or the furnace motor has problems.

Gas

• Natural gas is odorless, but gas companies add oderants, like mercaptan, to the gas to make it easier to detect gas leaks. If you smell gas, open the windows and leave the house. Don’t light any flames or use any light switches or electrical equipment, and don’t use the phone or the cell phone in your house because they could spark, causing an explosion. Call your gas company from a neighbor’s phone or outside on your cell.

Must/Mold

• Musty odors can occur when a house with a forced air heating system is built on a concrete slab and the air ducts embedded in the slab start acting like drain tile. The metal air ducts become corroded and mold can start to grow in them. Musty odors can also occur if the system is located in a mold-contaminated attic and the air ducts are pulling musty air into the air circulating system. If this is the case, you may need a new furnace or a redesign of your furnace system so the furnace is no longer connected to the ducts in the embedded concrete.