Why Is My Furnace Smelling Like Burning?

There are few things scarier for a homeowner than smelling smoke or burning inside their house. When you first turn your heater on for the winter, that distinct "burning" smell can set off alarm bells. But is it a fire hazard, or is it normal?

Here at Working Class HVAC, we get this call every year when the first cold snap hits Lancaster. Here is your guide to troubleshooting furnace smells.

The "Dusty" Burning Smell (Usually Normal)

If you haven't used your furnace in 6 to 8 months, dust has settled on the heat exchanger and burners. When you fire it up for the first time, that dust gets incinerated.

Verdict: Safe, usually. It should smell like "heating dust" and dissipate within 20-30 minutes. If it persists longer than that, or if there is visible smoke, turn it off.

The "Electrical" Burning Smell (Danger!)

Does it smell like melting plastic or ozone? This is NOT normal. This usually indicates an overheated motor, frayed wiring, or a failing electrical component.

Action: Turn off your furnace immediately at the thermostat and the breaker. Call a professional. Do not try to run the system.

The "Rotten Egg" Smell (Extreme Danger!)

This isn't a burning smell, but it's crucial to mention. Natural gas is odorless, but utility companies add a chemical called mercaptan to make it smell like sulfur or rotten eggs.

Action: If you smell this, you have a gas leak.

• Leave the house immediately.
• Do not use any light switches or phones inside.
• Call the gas company or 911 from a safe distance.

The "Musty" Sock Smell

This is usually "Dirty Sock Syndrome," caused by bacteria or mold growing on your coils. It’s not a fire hazard, but it is a health hazard and smells terrible.

Action: You need a professional cleaning of your evaporator coils and likely a UV light installation to prevent regrowth.