Chimney and fireplace symptoms
My fireplace smells, especially when it rains or the house is closed up
A fireplace that smells on damp Portland days often has creosote in the flue, stirred up by humidity. The odor is not a hazard by itself and a sweep removes it; a rotten note means an animal, so keep the fireplace cold.
Updated
What to do right now
Close the damper and any glass doors, then pay attention to when the smell peaks: after rain, on a muggy afternoon, or the moment a bath fan or the dryer starts. Open a window near the fireplace to take pressure off the flue. Skip the candles and deodorizers; they hide the signal we need to read.
Likely causes, most common first
What makes a cold fireplace smell on summer and rainy days, roughly from most likely to least.
- Most common
Creosote in the flue, woken up by humidity
The sign: A campfire or tar smell that is strongest on muggy days and after rain, from a fireplace that has not been lit in months.
The fix: A sweep strips the creosote from the flue walls, smoke chamber and shelf, removing the source instead of masking it. Chimney Sweep, from $249
- Common
The house is pulling air down the chimney
The sign: The odor arrives when the bath fan, range hood or dryer runs, or in a tight remodeled house with every window shut.
The fix: A top-sealing damper closes the flue with a gasket at the top, so the house stops drawing its makeup air through the chimney. Damper Repair and Replacement, from $149
- Common
Rain is getting into an uncapped or open-crowned flue
The sign: A musty, basement smell after a wet week, a damp smoke shelf, or water marks on the back wall of the firebox.
The fix: A cap over the flue stops rain falling straight down it, and a crown repair closes the slab it was soaking through. Chimney Cap Installation, from $299
- Less common
An animal, a nest or droppings on the smoke shelf
The sign: A sharp, rotten or barnyard odor that gets worse day by day, flies at the hearth, or scratching sounds behind the damper.
The fix: We remove the animal, or a nest no protected bird is using, clean and deodorize the smoke shelf, then screen the flue so it stays empty. Chimney Animal Removal, from $249
- Less common
Brick that stays wet through the winter
The sign: A damp, earthy smell from the chimney breast itself, with white salts or dark patches on an exterior wall chimney.
The fix: After the masonry dries out, a breathable water repellent on the brick keeps rain from soaking through to the inside face. Chimney Waterproofing, from $349
Two minutes of safe checks
Two minutes of nose work that narrows the cause before anyone climbs anything.
- Stand at the opening with the damper shut, then open it: a sudden wave means the flue is the source, a steady smell points to the firebox or the brick.
- Turn the bath fan and range hood off for an hour on a day the smell is bad; if it fades, the air balance of the house is driving it.
- Aim a flashlight at the smoke shelf from the hearth, without reaching in: damp soot, twigs, feathers or a dark water line each tell a different story.
- From the yard, check whether a cap sits on the flue; an open flue after a wet week smells musty for a reason.
- Name the smell: campfire or tar is creosote, a basement note is water, and a sweet, rotten edge is an animal.
Why a fireplace smells worse in July than in January
Creosote is tar, and tar smells more when it is warm and damp. A summer afternoon with the windows shut and the humidity up is the worst case, which is why a fireplace unused since March starts to smell in July.
In winter a lit fire pushes everything up the flue. In summer nothing is pushing, and bath fans, a range hood or an air conditioner put the house under slight negative pressure, so air comes back in through the open flue carrying the smell of the chimney walls.
Portland adds water. Roughly two thirds of the year's rain lands between November and March, and an uncapped flue swallows its share, so by June the smoke shelf is a damp pile of soot and the brick above it has been wet for months.
When the smell means stop and call
Book the visit instead of another candle when any of these fits.
- The odor is rotten or sweet rather than smoky; an animal that died on the smoke shelf gets worse, not better, and the flue stays cold until it is out.
- A smoke smell shows up while the fireplace is cold and a furnace or water heater shares the chimney; that can be flue gas, so check the carbon monoxide alarm on this floor and call before the next use.
- The smell began after a fire that roared like a freight train; that may have been a chimney fire, so if it is happening now leave the house and call 911, and afterward the flue needs a Level 2 inspection before it is lit again.
What getting rid of a fireplace smell involves
The visit follows the smell to its source and stops there.
Find the source
We smell and look before we brush: firebox, smoke shelf, damper plate, chimney breast and the cleanout at the base. A flashlight on the shelf usually settles whether it is creosote, water or an animal.
Sweep and clear the shelf
The flue and smoke chamber are brushed with the vacuum running, and the wet soot on the shelf is scooped out, since that damp pile holds much of the odor.
Close the flue properly
When the house is pulling air down the chimney, a top-sealing damper replaces the leaky throat plate, and the smell has no path into the room between fires.
Keep the water out
A screened cap goes on an open flue, and a crown repair or a breathable repellent follows where the brick itself was wet. Photos of each part come with the posted price.
Fireplace smells: common questions
Why does my fireplace smell bad in summer when I have not used it since winter?
Creosote left from winter fires smells more as the air warms and gets humid. A closed-up house with fans running then pulls that air down the flue. The fix is removing the creosote with a sweep, then closing the flue at the top so summer air stops coming down it.
Why does the fireplace smell worse when it rains?
Rain reaching the flue wets the soot and creosote on the walls and the smoke shelf, and wet creosote gives off far more odor than dry. An uncapped flue takes rain straight down; a cracked crown or open joints feed it through the brick. A cap and a dry smoke shelf end many rainy-day fireplace smells.
My chimney is capped, so why does the fireplace still smell musty?
A cap only covers the flue opening. Water still arrives through a cracked crown, open mortar joints or failed flashing, and an old throat damper does nothing to stop the odor of a damp smoke shelf drifting into the room. Check the firebox for water marks after rain; that points to the brick rather than the cap.
Will lighting a fire burn off a fireplace smell?
Not for long. A fire pushes the odor up the flue while it burns and leaves more creosote behind for the next muggy day. If the smell is an animal or a nest, a fire is also the one thing not to do; the material above the damper can catch, and a trapped animal cannot get out.
Does a fireplace smell mean something is wrong with the chimney, or is it only an odor?
It is a message. A creosote smell says the flue is carrying a layer that should come out; a musty smell says water is getting in somewhere; a rotten smell says something is on the smoke shelf. None of those is dangerous as a smell, but each points to a cause worth fixing before fall.
Can a smell from the fireplace be carbon monoxide?
Carbon monoxide has no smell, so a smell cannot confirm or rule it out. What a cold fireplace smell does tell you is that air is moving down the chimney into the house, and a furnace or water heater sharing that chimney can send flue gas the same way. Keep an alarm on the fireplace floor and have a shared flue inspected.
Related pages
Areas we cover for this
Calls about fireplace smells come in from King City, Oregon City, Sellwood-Moreland and every other part of the metro we serve.
Ready to book a sweep?
Call with what the fireplace is doing, or text a photo of the opening and one of the chimney top, and we will name the service and its posted price before we come out.