Why Does My Furnace Smell? A Closer Look

The US experiences roughly 370,000 household fires a year. Furnaces are an occasional cause of those (they deal with heat after all), so it’s natural to feel uneasy when your furnace smells strange.

Even outside of the possible dangers and whether you have an electric or gas furnace, you'll have to use it a lot this winter to keep warm. What do you do if your furnace isn't operating correctly?

Read on to learn more about what strange smells from your furnace could mean.

The Silent Danger of Furnaces

Strange furnace smells are vital signs of an approaching or ongoing furnace problem. Research shows that gas and oil-burning furnaces produce carbon monoxide (CO). It is an odorless, invisible toxic gas that kills hundreds of people each year and sickens thousands more. They may not be the best furnace type, safety-wise, so get them checked often.

Some furnace fragrances are natural; however, the smell of burning plastic, electrical aromas, or burning dust may indicate more severe problems with your HVAC system.

If this is the case, One Hour Heating and Air Conditioning is here to help you interpret furnace scents this heating season, explaining what each sort of odor signifies and when these smells suggest potential heating system problems.

Furnace Smells and What They Mean

If you notice a strange stench coming from your vents, you need not freak out! Furnace smells are not always a reason for alarm, and some aromas are natural. Decode the furnace stench you're experiencing with our guide below. With this knowledge, you’ll know when to call a professional and when you may relax and let the stink pass.

What Does a Functioning Furnace Smell Like?

As you use your HVAC system throughout the year, a fine coating of dust may collect within the heat exchanger, ductwork, and ignition system. Every season, you might notice a distinct burning smell when you switch on your furnace. It means dust in your system is burning off.

This odor may be unpleasant, but it should not last more than an hour and should not have a substantial influence on indoor air quality.

If you're concerned about the odor, you may open a window slightly to let some fresh air in or switch on a ventilation fan in a bathroom.

Other odors, on the other hand, might be a warning indicator. Natural gas is intentionally perfumed to smell like rotten eggs, and if you smell it, your system may be leaking.

Turn off your gas and contact 911 or your utility company. Mold and mildew can also indicate problems with your furnace since moisture issues can cause mold to grow within your ductwork.

Types of Smells That Furnaces Produce

The types of furnace smells are listed below:

• The odor of burnt plastic or electrical wire
• Metallic odor
• Burning dust or smoke
• Rotten eggs
• Mold or mildew
• Odor from pets
• Sludge

Do you know all of these odors are not directly created by your furnace? Read below to learn about them in detail.

Burning Dust Smell

The most typical stench you'll encounter when you turn on your home furnace for the first time in months is that of burnt toast or burnt cookies. A slight covering of dust collected immediately on the burner or heating element is most likely to blame. When you turn on your furnace, the dust burns off, resulting in that familiar odor.

Cleaning the burners or heating elements before use may help limit the possibility of burned particles. In contrast, the dust is relatively harmless since it will burn off within a few hours after your furnace is running.

After the dust burns off, there's a decent chance you won't have to worry about it for the rest of the season.

Burning Metals or Plastic

A burning metallic stench might point to issues with internal components. Maybe the metal casing of an overheated furnace can heat up to harmful levels. Electrical wiring can also overheat if too much current is carried through it, causing the wire insulation to melt or burn away.

Friction from worn bearings can also induce burning-metal scents before the entire engine seizes. Plastic cutlery and similar things are sometimes thrown near or into an operating furnace and might emit a burning plastic aroma.

You should immediately turn off your furnace and contact a professional for furnace services in any of these circumstances.

Rotten Eggs

Turn off your furnace right away if you get a whiff of anything that smells like rotten eggs or sulfur. Hydrogen sulfide (H2S) is a colorless gas with added rotten egg odor.

This scent often indicates a natural gas leak, which might endanger your entire home if left uncontrolled.

You should not only switch off your furnace as quickly as possible, but you should also walk outside and notify your local gas company or fire department so that they can deal with the leak. If the situation persists, they may send someone to assist.

Pet Smells

At times, the stench of pet excrement or hair may appear to originate from the furnace registers. If you notice a strong odor whenever you switch on the furnace, you should examine the floor-level ventilation registers. The problem gets resolved by cleaning up the mess near the vent.

Sludge Smell

If you smell sewage water coming from the vents, an open sewer line or a damaged wastewater line may be close to the system. A brief check of the external vents might assist in determining the source of the odor. To address the problem, you may need to contact a plumber.

Dingy Laundry

Sometimes you switch on your house furnace for the first time, you don't detect the distinctive smell of a leak in progress but rather a slightly damp, musty scent.

The stink may lead you to believe that there is a concealed pile of dirty, sweat-soaked garments someplace in your home. When your furnace and air conditioner share the same air-handler cabinet, mold, mildew, and bacteria frequently grow inside the HVAC system, causing the smell.

During the summer, while you run your air conditioner, the relatively damp and gloomy confines of your air-handler cabinet might accidentally favor mold and bacterial development.

The evaporator coil and condensate drip indicate tray are frequently prime places for development. When you turn on your furnace after months of unregulated development, you may notice a peculiar, musty stench when the growth dries and warms up.

The easiest way to get rid of a musty furnace is to have your HVAC technician thoroughly clean the evaporator coil and condensate drip tray. They disinfect these areas to eradicate any leftover growth. A germicidal UV lamp put within the air handler can prevent the formation of germs and mold for the future.

Mold or Mildew Smell

A moldy odor emanating from the furnace suggests mold infestation inside the ductwork. You should not take mold infestation lightly. Mold may wreak havoc on the quality of indoor air. It has the potential to create flu-like symptoms such as sneezing and coughing.

A professional service will remove mold and mildew from the ductwork and take precautions to guarantee that it does not reoccur.

Burning Oil Smell

An oil odor indicates that your furnace filter is blocked. Replace your house furnace filter every three months, but change it more often if your home has pet hair, smoking, or heavy dust. The burning oil scent should go away once you replace your filter.

Smoke Smell

If you notice a smoky odor emanating from your furnace, switch it off immediately and open a couple of windows. It can happen if the furnace chimney (also known as a "flue pipe" or "exhaust vent") becomes clogged. The combustion exhaust from the furnace has to go someplace, so it goes into the ductwork.

Chemical Smell

It is one of the most harmful odors you may encounter in the comfort of your own home. If the odor is prominent and comparable to formaldehyde, there is most likely a fracture in the heat exchanger component of your furnace.

The heat exchanger component circulates heat from the combustion chamber to the plenum. If this component fails, the risk of fire is significantly increased. It might potentially spread carbon monoxide emissions throughout your home too.

How to Repair a Smelly Furnace?

A furnace has a high heat retention capacity, is simple to maintain, and is entirely safe to use. But, you must have some routine maintenance performed to remedy an unpleasant smell emanating from your furnace. Some of these you can do yourself, such as:

• Before turning on the heating unit, remove any dust or debris accumulated on the coils, heater exchange, or the interior of the heating unit
• Replace the furnace filter
• Examine the ducts for dirt and dust. You may even use a vacuum to get rid of them

Call a Professional Today

Abnormal furnace smells emanating from your home might indicate a failed or damaged system. If you detect weird furnace smells when you first switch on your heater, it's time to figure out what's wrong and fix it as soon as possible.

Request an appointment today to fix any potential issues before they get out of hand.