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Why Fireplaces Smell (& How To Fix It)

Sometimes our fireplace smells up our house. Generally, this is in the summer, especially after it rains. We wanted to find out what was causing it and how to fix it, so we did some research. Here’s what we found.

Fireplaces become smelly from air pressure, humidity, creosote, bad wood, and animal nests in the chimney cap. Ideally, get your fireplace inspected and cleaned once a year and close the damper when you don’t have a fire running. If your fireplace has glass doors, consider closing them when there’s not an active fire.

Now, let’s take a closer look at what causes fireplaces to smell and exactly how to fix it.

Pro-Tip: For the hottest and longest fire, only burn firewood that contains less than 20% moisture content. To find out how dry your logs are, I recommend using a moisture meter.

What are Fireplaces Supposed to Smell Like?

a lit fireplace

You can learn a lot from the smell of your fireplace. If you have a regularly cleaned and well-maintained fireplace, there should only be a faint smoky odor left behind directly in the firebox. This should also only be detectable if you are up close to the fireplace. 

On the other hand, if the entirety of your house smells like an active Boy Scout campsite, you might have a problem. It’s expected for some odors to be here and there if you use a fireplace. However, it’s important to know what’s considered normal and what’s unusual or poses a safety issue.

Fireplace odors can mean signs of poor maintenance, lack of cleaning, or other issues. They may also just be caused by weather patterns that are outside your control. 

The odor from a fireplace comes from the creosote and ash deposits that get embedded into the masonry structure around the fireplace and chimney.

Regardless of how skilled your chimney sweeper is, it is impossible to remove every piece of creosote and ash. If you have a poorly maintained fireplace and chimney, you are likely going to get significantly more odors.

These odors will generally smell like a smoky campfire and will get worse depending on your chimney’s maintenance situation.

If you’re detecting a chemical odor, you or a family member may have burned something that should not be burned (e.g. certain types of paper with ink, plastic, trash, etc).

5 Reasons Fireplaces Smell Bad

1. Air Pressure

One of the major causes of bad smells comes from imbalanced air pressure and drafts. If air is coming down your chimney, instead of up, this may be a problem caused by the cap on top of the chimney or improper damper closures.

The more unfortunate situation may be due to your geographical location and having a chimney in just the wrong spot on your house. One of the solutions is to have a certified professional inspect your chimney.

2. Humidity

The wet air that comes in from the outside is heavier than the air inside your house. Therefore, this will create something called the “stacking effect.” This effect essentially pushes the smelly air in a creosote-filled chimney back into your home. This effect also happens when it rains for the same reason. 

Recommended: Can You Use a Fireplace When It’s Raining?

3. Creosote Build-Up

creosote in a stove pipe
Creosote in a stove pipe.

Creosote is a deposit of tar from the smoke and is normal to have in fireplaces and chimneys in small to moderate amounts. However, burning unseasoned (green) wood or sappy wood can lead to more creosote.

Generally, the more creosote you have in your chimney, the worse the smell. Not only does this cause a bad odor the longer it lingers, but it’s also a fire issue if left uncleaned.

4. Burning Bad Wood

Sometimes people throw things in a fireplace that should not be burned.

Whether it is an old rotten log, a plastic toy, or anything that is not clean and dry firewood, you’ll experience an unpleasant odor. Depending on what type of material gets burned, this smell may linger longer than others.

Always be mindful of what is going into the fireplace and who has access to the fire, and be sure to do some basic research on what can or cannot be safely burned.

5. Animals Nesting

a bird nesting on a fireplace chimney

Occasionally, you may find an animal nesting in your chimney cap. Birds and squirrels are the most common to find here, but other animals have been known to make nests at the top of chimneys.

These nests can contribute to the smell of chimneys, which is carried into your house when there’s a draft.

Why Fireplaces Smell After It Rains (& In The Summer)

You’ll smell differences in odor depending on the weather. Whenever it’s humid or raining, expect a downdraft to push through your chimney and carry bad odors into your home.

Downdrafts are also a problem when you have an active fire burning, as you may see smoke pushed into your home.

The location of your fireplace in your home may also have a considerable impact on the staff effect, which creates downdraft into the home.

For example, the basement is considered a low-pressure zone, whereas the higher stories of your house are considered high-pressure.

With a fireplace in the basement, you will have a longer chimney that creates more space available for outside pressure to exert its forces.

It’s ideal to place a fireplace on the neutral pressure floor, which is typically the first floor

Regardless of the fireplace location in your house, it’s still subjected to the same external forces such as humidity and rain, just at varying levels. Similar to how warm air pushes against cold air, it will push against humid air as well.

This shoving contest between heated indoor air and heavy outdoor air is going to put your fireplace in the middle of it and cause downdraft.

Even if you don’t have a fire burning, the humid air still pushes its way down your chimney and brings along the smell of creosote and ash particles.

5 Ways to Get Rid of Fireplace Smell

1. Get a Professional Inspection

There’s nothing wrong with being a DIYer, and it’s not a bad idea to try troubleshooting the situation yourself first.

But when it comes to safety, it’s a good idea to get a professional opinion. A certified professional may be able to spot issues that an untrained eye cannot see.

They can also provide you with the input and advice needed to quickly fix the issue, sometimes at a cheaper cost (in both time and money) than doing it yourself.

2. Clean Your Chimney

a chimney sweep cleaning a chimney

One of the most common solutions to eliminate any odor in your house is to tidy things up, and this includes your chimney.

Fireplaces and chimneys should be cleaned annually or when the creosote buildup is greater than 1/8 of an inch. It’s recommended to hire a professional to inspect and clean your chimney.

A thorough chimney cleaning greatly reduces odors caused by downdrafts. It will also reduce the risk of a chimney fire. Additionally, you cannot neglect the fireplace itself.

The area in which you burn the logs should be vacuumed with a special ash removal vacuum. A normal vacuum will quickly break if used for fireplace ashes. Make sure the ashes are cool to the touch to reduce risk.

3. Close The Fireplace Damper When Not In Use

The parts of a fireplace
Image source: Camosse Masonry Supply

If it’s humid outside, and you have a tight-fitting damper, closing it will reduce the odor. The humid air will have less opportunity to push the chimney’s air back into your house if the damper is closed.

However, if this is something you’re already doing and you’re still dealing with odors, consider visually checking the damper to ensure it is not leaky or malfunctioning.

Recommended: When Should You Close the Damper on a Fireplace?

4. Install a Top-Sealing Damper

This is a secondary damper you can have installed at the top of your chimney. Consider it like a second door to keep out the humidity when not in use. This top-sealing damper is controlled through the fireplace with a metal cable.

5. Install a Glass Screen

Glass screens are useful in preventing odors when you don’t have a fire going. However, if the doors are closed while burning, it reduces oxygen access to the fireplace.

As a result, the temperature of the fire will be reduced and the humidity from the outdoors may cause downdraft and a smoke-filled house.

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