Problems & Repairs
Chimney smells are one of the few faults where the symptom genuinely tells you the cause. A sour, ashtray-like smell in warm weather is a different problem from a sharp, tarry smell after rain, and they need different work.
Almost all of them come down to two things: deposits inside the flue, and air moving down the flue instead of up it.
The summer smell: deposits plus humidity
The classic complaint is a fireplace that smells worst in July. Soot and creosote are hygroscopic, meaning they absorb moisture from humid air, and wet deposits release odour that a dry flue does not.
This is the easiest version to fix. A thorough sweep removes the material producing the smell, which is why we recommend a summer sweep for anybody who has noticed it.
The downdraught smell: air coming the wrong way
If the smell arrives with the wind, or when the extractor fan is on, the flue is being used as an air inlet. Modern homes are far more airtight than the houses these chimneys were built for, so when a fan or a tumble dryer pulls air out, the easiest replacement route is down the chimney.
Fixes here are about pressure rather than cleanliness: a suitable cowl, adequate ventilation, or sealing an unused flue correctly while still allowing it to breathe.
The damp smell: water entering the stack
A musty smell alongside staining on the chimney breast means water is getting in. Failed flaunching, cracked pots, missing flashing or a redundant flue with no terminal are the usual routes.
Water in a sooty flue makes an acidic mixture that attacks mortar from the inside, so this one gets worse if left. A camera survey shows where the wet is entering.
The one to take seriously
If you can smell combustion gases while the appliance is alight, stop using it and ventilate the room. That is a spillage problem, not an odour problem, and carbon monoxide itself has no smell at all. Fit and test a CO alarm regardless of whether you smell anything.
Frequently asked questions
Will sweeping definitely stop the smell?
It fixes the deposit-related smells, which are the most common. If the cause is downdraught or water ingress, sweeping alone will not solve it, and we will say so rather than take the money and leave you with the problem.
Can I block the chimney up to stop the smell?
Not with anything airtight. A sealed flue traps moisture and rots from the inside. If a flue is genuinely redundant it should be capped and vented so it can still breathe.
Why is it worse when the heating is on?
Central heating warms the house and increases the pressure difference between inside and out, which can draw air down an unused flue and bring the smell with it.
Does a cowl help?
An anti-downdraught cowl helps considerably where wind is the cause, and a capped and vented terminal helps on a disused flue. Neither helps if the real issue is heavy deposits.
Is the smell dangerous?
The smell itself usually is not, but it can accompany a spillage problem that is. Carbon monoxide is odourless, so never use smell as your safety indicator. Fit an alarm.
Get the cause identified properly
A sweep and a camera check settle most chimney smells in one visit. Book a slot and we will tell you which of the three causes it is.