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Furnace Smells: How to Reduce or Eliminate Odors in Your Air Ducts

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Dan has been in the HVAC industry for 23 years, with experience ranging from installation and service to sales and distribution.

Plants are still a great way to help air quality in your home and add some beauty at the same time.

Plants are still a great way to help air quality in your home and add some beauty at the same time.

Common Causes of Furnace Odor

Everyone likes the air in their home to smell fresh and clean. Many even want it to smell apple-ish, or lavender-ish, or even patchouli-ish, but no one I've ever known has said, "I love the musty smell my furnace provides." Look no further than the candle and air freshener market these days for proof that people like things to smell good.

There are whole stores dedicated to making your surroundings smell better, however not all issues can be solved by making a trip to Yankee Candle. Your furnace and ductwork are a couple of those issues. Knowing some of the common causes of furnace odor may help in resolving your issue, so let's take a look at some of the things that cause these unpleasant smells in our home.

Things That Cause Our Ductwork to Stink



Aside from the fact that dust itself has an odor, when the furnace runs it burns that dust that has built up in the off season and blows it through the air ducts.

Having your furnace and evaporator coil cleaned before fall cold arrives.

Dead Animals

Animals like to be warm. More than a few birds and chipmunks have met their end in chimneys and inducer fans as well as mice and other rodents looking to make nesting material out of filters, wiring, and flexible air ducts.

Remove dead animal. Most commonly found in the flue pipe, inducer fan, blower compartment, and occasionally the ductwork itself. Signs of damage can help you locate the deceased if there is one.

Mold / Mildew

Most often found in underground ductwork, mold and mildew are a very common cause of bad household smells. Time often allows water to leak into these systems and create all kinds of bad odor as well as health concerns. Evaporator coil drain trays and drains can contain mold and mildew as well as unattended humidifiers with old water panels.

Having your humidifier, evaporator coil, and ducts cleaned is the most surefire way to handle this problem however if you have an underground system, it's not nearly that simple and you may have to consider having your ducting lined or sealed by a professional since once they leak, they always will.

Part Failures

When electrical parts fail they often overheat or "burnout" thus creating the distinct odor of melting plastic or burnt wires.

Even if your unit is working, you may have a motor or other electrical part overheating and getting ready to fail. Have this checked out before it's an issue.

Whether metal or plastic, it's not uncommon for older underground ducting to take on water. New codes have helped minimize this risk but with settling and age, it's hard to guarantee.

Whether metal or plastic, it's not uncommon for older underground ducting to take on water. New codes have helped minimize this risk but with settling and age, it's hard to guarantee.

HVAC Products That Improve the Smell and Quality of Air in Your Home

HVAC technology offers homeowners a lot of product options for improving the quality and smell of the air in our homes. These IAQ products have drawn extra attention in today's world where our homes are sealed up so tightly. Let's start by taking a look at some of the products available to us that can be installed in our HVAC systems.

Indoor Air Quality Products

Ionization technology, though not new, has made progress in providing smaller, easy to install units for residential and commercial applications. This is quickly becoming one of my top suggestions for those looking into IAQ improvements.

Product CategoryDescriptionProsCons

Media Filters

These are filter cabinets installed in our return air duct with a larger (wider) surface area that catch much more dust than the typical 1" wide filters most of us use.

Much lower amounts of dust in a home compared to a home with a standard 1" filter.

Filter replacements are more expensive and ductwork may need modified to accomodate air flow restriction and installation.

Electronic Air Cleaners

Providing the same advantages as a media filter, these also use electricity to zap dust particles as well.

Provides the best dust control of air filtering products.

Initial costs is higher than other air cleaners and routine maintenance is required to keep it functioning at full capacity. Electrical components mean there is potential for breakdowns.

UV Lighting

Lamp installed onto / into your duct work, typically above the evaporator coil, lights up the inside of the duct with UV light.

Provides healthier air in the home by using UV to kill pathogens and microorganisms..

Requires some maintenance including bulb replacement from time to time and only treats the area exposed to the light.


A small ion producing unit usually wired into the blower and sits in the furnace cabinet.

Provides the benefits of other IAQ products in one unit that requires little to install and no maintenance.

Cost. These are not cheap.


A separate unit tied into your ductwork requiring it's own space and duct to outside of home.

Fresh outdoor air is filtered and brought into the home as well as exhausting stale, perhaps radon or VOC filled air.

Cost. These units are not cheap either and require a fairly extensive process to install. Maintenance and filter changing is a must.

Did You Know . . .

. . . running your furnace fan continuously (in "fan" mode) will keep the air in your home circulating, thus passing through the filter and in turn provide cleaner air? This helps even out the temperatures of the house as well.

Like the smell of  Gain? Try putting a dryer sheet on your filter. Scented or non-scented, dryer sheets are great for absorbing odors.

Like the smell of Gain? Try putting a dryer sheet on your filter. Scented or non-scented, dryer sheets are great for absorbing odors.

Cheap Tricks to Make Your Home Smell Better

Not everything you do to improve your home's air quality and smell has to cost you a bunch of money. There are a few tricks I've learned and some rather easy things anyone can do for themselves that can make a significant difference in this arena.

Keep in mind these aren't permanent fixes of underlying problems (such as not removing a dead critter or treating mold and mildew issues) but they're great for maintaining a pleasant atmosphere at little to no cost.

  • Placing a dryer sheet on the incoming side of your filter helps absorb odor and if scented, can add a bit of a pleasant smell to the air.
  • Placing an air freshener like what you might use in your car in the same manner as the dryer sheet.
  • Vacuuming out the furnace's blower cabinet and the duct on the incoming side of your filter. (May as well since you're putting an air freshener there anyway)
  • Placing dryer sheets or air fresheners inside your registers. May as well sweep these too while you have the vacuum out.
  • Make sure the area surrounding your furnace is clean and odor-free. Since most systems are not airtight, dank basement, crawlspace, attic, or closet air can be pulled into the ductwork and pushed into the rest of the home.
  • Don't forget about plants in the home. Though some are more effective at this than others, they all help some and are pretty too.
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Read More From Dengarden

I'd love to hear of other ways you might have thought of to freshen up the air in your home. Leave me a comment if you'd like to share your ideas with the rest of us.

Did You Know . . .

. . . if you lay a few dryer sheets on top of, spilled milk for example, then place coffee grounds on top of them it will help absorb the spill and odor that tends to linger?

We're starting to keep a lot of this ClenAir by Nu-Calgon on had for HVAC call-outs regarding bad smells. It works very well.

We're starting to keep a lot of this ClenAir by Nu-Calgon on had for HVAC call-outs regarding bad smells. It works very well.

Sometimes no matter what you do, or how clean you get the ducts, you still have bad smells that just won't go away. These smells built up over time in all the crevices and cracks throughout your system.

When nothing else works, a lot of us in the HVAC industry are now starting to use this ClenAir Odor Neutralizer. In fact, we use this extensively on restorations after fire or flood damage to get out the last bit of remaining smell. Just stick it in the air return and it'll do the rest.

A Clean-Air Home Is a Healthier Home

Getting rid of nasty odors in our home is obviously something we all want to do if we are experiencing this type of thing but the underlying truth here is that if you have bad odors in your ductwork, your entire home is affected and it's usually not without cause. These causes not only make things smell bad but often can jeopardize our health as well.

I hope you found something here that not only helped create a more pleasant smell in your home but maybe even provided a healthier atmosphere for you and yours. We're all in this together!

  • How to Clean a Smelly Refrigerator
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  • How to Cross Ventilate Your Home
    Cross ventilation can clean your home's air, save you money and is easy to create without spending money. Start breathing cleaner air and saving money today.
  • How to Clean Air Ventilation Ducts Yourself
    Cleaner duct work equals cleaner air and less dusting. Learn how you can improve the quality of the air in your home for free without specialized tools.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2018 Dan Reed


Shelly on August 24, 2018:

Excellent article.

Dan Reed (author) on June 06, 2018:

Rich - I don't recommend doing this. Lysol disinfectant contains very harmful chemicals. It is flammable and dangerous to inhale. If you look up "Lysol disinfectant spray warnings" you'll see this for yourself. I'm not a big fan of the product. I know you've been using it but once you read up, you may change your mind about continuing this practice.

Rich on June 05, 2018:

Annually I spray a generous amount of Lysol disinfectant directly up through my evaporator coil with just the fan running to distribute it through the ductwork. Then I turn off the fan and let it sit for an hour before turning the fan back on with all windows open to ventilate the house. This seems to get rid of moldy, musty odors from our attic ductwork.

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