Guide
Signs your chimney needs sweeping
Updated
The short answer
Your chimney needs sweeping if smoke comes back into the room, the fire is hard to light or won't draw, there's a smell of soot (especially in damp weather), black flakes or debris fall into the grate, or it's been more than a year since it was last swept. If you hear birds in the chimney, don't light the fire.
Smoke coming into the room
If smoke drifts back into the room instead of going up the chimney, something is narrowing the flue: soot and tar, a nest or fallen debris. Don't keep using the fire until it's been looked at, because the same blockage that sends smoke into the room can let carbon monoxide build up.
A fire that won't draw
A fire that's slow to light, burns poorly or keeps going out often isn't getting enough air through the flue. A build-up in the chimney is one of the most common causes.
A smell of soot
A sooty or tarry smell in the room, especially when the weather is damp and the fire isn't lit, usually means deposits have built up in the chimney.
Debris in the grate
Black flakes, lumps of soot, twigs or bits of mortar landing in the grate are coming from inside the chimney. Twigs in spring often mean birds are nesting, which needs handling outside the nesting season.
You can't remember the last sweep
If you don't know when it was last done, or you've just moved into the house, have it swept before you rely on it for the winter.
Questions
Can a dirty chimney cause a chimney fire?
Yes. Tar and soot that build up in the flue can catch fire. Regular sweeping and burning dry fuel are the main ways to prevent it.
What should I do if I hear birds in the chimney?
Don't light the fire. Nesting wild birds are protected, so the nest has to wait until the nesting season is over. The National Parks and Wildlife Service (npws.ie) has the rules.