Why Does My Fireplace Smell in the Summer?

It is July in Dallas. It is 100 degrees outside, you have not lit a fire in five months, and your living room smells like a wet campfire. You are not imagining it, and you are not alone. Summer fireplace odors are one of the most common calls a chimney company gets.

The short answer: heat and humidity make the creosote and soot inside the chimney smell stronger, and your air conditioner pulls that smell into the house.

Where the Fireplace Smell Comes From

Every wood fire leaves a byproduct on the inside of the flue. Soot is the dry, black powder. Creosote is the darker, tar-like coating. Both have a strong, smoky smell.

In winter you do not notice it, because warm air rises up the chimney and takes the odor with it. In summer, three things change.

1. Humidity wakes up the creosote

Creosote absorbs moisture from the air. Dallas summers are humid, and damp creosote smells far stronger than dry creosote. That is why the odor is worse on muggy days and after a storm.

2. Your air conditioner creates negative pressure

A modern house is sealed tight. When the air conditioner, the kitchen fan, the bathroom fans and the clothes dryer run, they push air out of the house. New air has to come in from somewhere. The easiest path is often the chimney.

So air flows down the chimney instead of up. It passes over the soot and creosote, picks up the smell and carries it into your living space. This is called negative pressure, and it is the reason a fireplace smells even when it is not in use.

3. Rain gets in

If the chimney has no cap, rain falls straight down the flue. Water mixed with creosote makes a sharp, sour odor. A musty smell, like a damp basement, means water is getting into the brick through a cracked crown or loose flashing.

What Each Fireplace Smell Means

• Smoky, like a campfire or barbecue: creosote and soot in the flue.
• Musty or damp: water is getting into the chimney.
• Rotting or sour: leaves, a nest, or an animal that died in the flue.
• Rotten eggs near a gas fireplace: this may be a gas leak. Leave the house and call your gas company from outside.

How to Get Rid of the Smell

Have the chimney swept

Remove the source. A professional chimney cleaning takes the soot and creosote off the walls of the flue, the smoke chamber and the firebox. For most homes, this alone ends the odor. Our chimney cleaning service in Dallas includes a camera check of the flue and a photo report.

Make sure the damper seals

A damper that is rusted or warped leaves a gap for air to come down. If yours will not close tightly, a top-sealing damper closes the flue at the top of the chimney with a rubber gasket. See damper repair.

Install a chimney cap

A cap keeps rain, leaves and animals out of the flue. Less water means less smell. See chimney caps.

Fix the leak

If the smell is musty, cleaning will not solve it. The water has to be stopped at the crown, the flashing or the brick.

Give the house another way to breathe

Sometimes the fix is as simple as opening a window a crack near the fireplace when the kitchen fan is running, so the house pulls air from there and not from the chimney.

What Does Not Work

Baking soda, kitty litter, vinegar bowls and scented candles cover the smell for a few days. A fireplace plug or chimney balloon can block the airflow, but the creosote is still in the flue and still a fire risk. You must remember to remove any plug before you light a fire.

Why Summer Is the Right Time to Deal With It

A smell in July is your chimney telling you it needs attention before winter. Summer and early fall are also the easiest time to book. Once the first cold front hits Dallas, every chimney sweep in town is busy.

The Chimney Safety Institute of America recommends a yearly inspection for every chimney, whether you burn a lot or a little.