Chimney & Fireplace Problems
Chimney or Fireplace Smells
A smell from a fireplace is almost always creosote, moisture, or something that got in. Which of the three it is tends to show in when the smell appears.
What You Are Actually Smelling
The sharp, tarry, campfire-gone-wrong smell most people describe is creosote — the residue wood smoke leaves on the flue walls. It is there all year, but it is not always noticeable, and the reason is humidity.
Creosote releases far more odor when it is damp and warm. That is why a chimney that seems fine all winter starts to smell in July, and why the smell arrives after rain: the deposits have taken up moisture and are giving it back off into the house.
The other two causes are simpler. Water sitting somewhere it should not produces a musty, damp smell rather than a tarry one. And an animal, a nest or accumulated organic debris in an uncapped flue produces exactly what you would expect.
When the Smell Appears Tells You a Lot
Timing is the most useful diagnostic you have, and it costs nothing to observe.
Worse in warm, humid weather
Creosote. Humidity is what releases the odor from the deposits.
Worse after rain
Either creosote taking up moisture, or water getting in somewhere it should not.
Worse when the air conditioning is on
Negative pressure pulling air down the flue instead of letting it rise. The smell was always there; the airflow changed.
A musty, earthy smell rather than a tarry one
Moisture rather than creosote. Points at the crown, the cap or the flashing.
A sharp, unmistakably organic smell
Something got in. Usually via an uncapped flue.
Constant, regardless of weather
Worth a look — a persistent smell that does not vary is less typical and less easily explained.
Why the Smell Comes Down Instead of Going Up
A chimney only pulls upward when there is something warm in it. With no fire burning, the direction of flow depends on the pressure difference between the house and the outside — and in summer, with the house cooler than the air outside and an air conditioner running, that difference frequently runs the wrong way.
So the smell is not usually a sign that anything has changed in the chimney. It is a sign that the airflow reversed, and the deposits that were always there are now venting into the room instead of out of the top.
That is why a top-sealing damper often helps more than anything else: it closes the flue properly when it is not in use, where an old throat damper rarely seals at all.
What Actually Helps
Cleaning removes the deposits producing the odor, and it is the right first step where creosote is the cause. It does not always eliminate the smell completely — creosote soaks into masonry over years — but it removes the source of most of it.
Where the smell is moisture, cleaning will not help and the answer is finding where the water is getting in: the crown, the cap, the flashing or the masonry. Where it is something that got in, clearing the flue and then capping it stops the next one.
What does not help is a deodoriser. Masking a chimney smell leaves whatever is producing it in place, and if that is water it will keep doing damage while the room smells fine.
A smell of gas is not this. If you smell gas, leave the property, do not operate switches, and contact your gas supplier or emergency services from outside.
Frequently Asked Questions
Why does our chimney only smell in summer?
Two things happen at once. Humidity releases far more odor from creosote deposits, and air conditioning tends to put the house under negative pressure so air comes down the flue instead of going up it. The deposits were always there; summer is when you notice them.
Will cleaning get rid of the smell?
It removes the source of most of it, which is usually enough. Creosote also soaks into masonry over years, so a very long-standing smell may reduce rather than disappear entirely.
It smells musty rather than smoky.
That points at moisture rather than creosote, and cleaning will not address it. The question becomes where water is getting in — the crown, the cap, the flashing or the masonry — and that is a leak investigation.
Would a better damper help?
Often substantially. A top-sealing damper closes at the top of the flue against a gasket, where an old cast iron throat damper rarely seals at all. It stops the reverse airflow that brings the smell into the room.
Can I just use something to mask it?
You can, and it is worth knowing what you would be masking. If the cause is water, the smell is the only signal you are getting about damage that is continuing, and covering it up is genuinely counterproductive.
What Deals With a Chimney Smell
Chimney Cleaning
Removes the creosote deposits producing most chimney odor.
Chimney Damper Repair
A top-sealing damper stops air coming down the flue when there is no fire.
Chimney Leak Repair
Where the smell is moisture rather than creosote.
Chimney Cap Installation
Keeps rain and organic debris out of the flue in the first place.
Chimney Inspection
When the cause is not obvious from the pattern.
Animal or Bird in the Chimney
Where the smell is unmistakably organic.
Request a Free Estimate
Chimney Smell You Cannot Place?
Tell us when it is worst — humid weather, after rain, or with the air conditioning running. Timing points at the cause more reliably than the smell itself does.
- Tell us the symptom, not the service
- No quote before someone has looked
- No obligation, no pressure
Describe the Problem
A few details is all we need to get started.