Smoke odors from the furnace are often harmless, but they aren't something that you want to ignore. Know the common causes so you can troubleshoot the issue and schedule the proper repair.

1. Dust Issues

Dust in the system is one of the more common causes of burning odors. This type of odor tends to only occur right after the furnace turns on, especially at the beginning of the heating season. The odor could be in the ducts or on the burner inside the furnace. In some cases, it's caused by a dirty air filter that needs to be changed. If the smell is mild and dissipates quickly, it's usually nothing to worry about. However, if the smell lingers, you may want to schedule an inspection.

2. Electrical Short

An electrical short is a more concerning problem. Burning from electrical issues may have a metallic odor, particularly if it is causing sparks to jump somewhere in the system. In some cases, there may also be the odor of burning or melting plastic. This typically indicates that the main circuit board is experiencing shorts. If you suspect electrical concerns are causing the odor, shut down the furnace and schedule an immediate repair visit.

3. Dirty Burner

Although a bit of dust on the burner is normal, especially when you first fire up the furnace in the fall, the burning odor should dissipate quickly and not return. In some cases, though, the burner is very dirty and the burning odor will persist throughout the heating cycle. Leaking valves can result in a sticky residue that traps excessive dust. Each time you turn on the furnace you will experience the odor as the excess fuel inefficiently burns off. Your tech will have to repair any leaks and thoroughly clean the burner.

4. Clogged Oil Filter

For oil furnaces, a burning odor could be a sign that the oil filter is clogged. Impurities in the oil are making their way to the burner, where they can't burn off cleanly. The result is the smell of burning oil penetrating throughout your home. A filter replacement usually fixes the issue, but if it keeps occurring frequently then you may need to have the oil tank inspected. Sometimes sludge can build up in the tank, which leads to more impurities in the fuel. Cleaning the tank and replacing dirty fuel lines can usually solve the problem.

5. Blower Burn Out

The blower motor can suffer many mechanical issues, which can lead to smoke and burning odors. Friction in the motor or fan from poor lubrication or failing bearings is a common complaint. The motor itself can also age and begin to burn out, which will often result in smoke and the accompanying odors. Some blower issues are repairable while others necessitate the installation of a new blower.

To learn more, contact a furnace repair service near you.