Why Does My Furnace Smell Like Gas? This (And Other Bad Smells) Solved

Are you wondering, “why does my furnace smell like gas?” or any other bad smell? You’re not alone. This is actually rather common, and there are several reasons for why it happens.

Some scents often indicate unit damage or failure; therefore, it’s important to understand the possible causes of these odors and what they mean, so that you can tap in the right professional to solve it. 

1. Natural Gas Leak

If you smell an odor similar to rotten eggs or sulfur, you may have a gas leak in your home. Natural gas is dangerous when inhaled, and can cause nausea, fatigue, and difficulty breathing. If you notice this smell, you need to take immediate action. 

In fact, natural gas has no odor of its own; many gas companies add the odor-creating chemical as a safety precaution. This substance gives off an unmissable smell, so that you know when natural gas is leaking. 


Due to the health and safety risks, you should never try to pinpoint the source of this odor on your own. Call a professional immediately, and exit your home until the area is clear of the gas.

2. Bacteria Build-Up

Known as “dirty sock syndrome,” the build-up of bacteria and mold from organic materials on your heating coils can cause a bad odor. During spring and fall, the coils cool when the temperature drops. However, they then reheat when you turn up the thermostat in colder weather.

This back-and-forth cycle between warm and cold can result in moisture buildup, resulting in bacteria growth.


The best way to eliminate this issue is proper cleaning. Start by replacing the filter in your unit and cleaning the coils with a non-acidic coil cleaner. 

If the smell doesn’t go away, you should contact an HVAC technician to thoroughly clean your air ducts (and possibly the rest of your unit).

3. Your Unit is Overheating

Typically, an odor similar to that of chlorine or metal indicates that your unit is too hot. As your furnace ages, the blower motor may seize up. This can cause your furnace to draw additional electricity, resulting in excessive heat buildup. 

The heat can be enough to melt wire insulation, which can cause your unit to produce electrical shortages or sparks that emit that metallic odor. In some cases, this can even start a fire.


If you smell electrical burning, you should turn off the power to your unit and call an experienced technician for help as soon as possible to eliminate the risk of fire or smoke.

4. Must (Or Dust)

If your furnace goes an extended amount of time without running, it may start to emit an odor similar to a damp, dusty basement. This musty smell occurs when dust, dirt, rust, or other debris collect within your unit and in your air ducts. 

As your unit warms, the dust and dirt may burn and smell slightly smoky. However, don’t panic.

If the smell persists, the filter could be clogged, which allows dust and dirt to reach your motor. 


Check your air filter and replace if needed, or call an HVAC technician to inspect your unit.

Why Does My Furnace Smell Like Gas? Let Us Solve The Problem

If you smell an odd or foul odor coming from your heating unit, don’t hesitate to reach out for help. Our expert HVAC team offers 24 hour emergency service to help you and your family live safely in your own home.

Contact us, and our HVAC technicians will handle it!