A simple guide from Alfred Poppins – Chimney Sweeping & Stove Specialists
What is a cold plug?
A cold plug happens when a column of cold, dense air becomes trapped in the chimney flue. This cold air blocks the warmer air from rising, preventing the stove or fireplace from drawing properly.
Cold plugs are most common:
- In unused chimneys
- During very cold weather
- At the start of the heating season
- In well-sealed or modern homes
Signs you may have a cold plug
You might notice:
- Smoke coming back into the room
- The fire struggling to light or stay lit
- A strong smoky smell indoors
- The fire only working once the room is very warm
If this happens, do not continue lighting the fire, as smoke and fumes can enter the room.
How to Clear a Cold Plug Safely
1. Check ventilation
Before lighting the fire:
- Open any air vents
- Slightly open a window near the stove or fireplace
This helps fresh air enter the room and improves airflow up the chimney.
2. Warm the flue gently
The safest way to clear a cold plug is to gently warm the air inside the chimney:
Option A – Kindling method
- Roll up a sheet of newspaper into a torch shape
- Light it and hold it up inside the stove or fireplace (near the flue outlet)
- Let the warm air rise for 30–60 seconds
Option B – Small fire method
- Light a very small fire using dry kindling only
- Keep the stove door slightly open at first
- Once the smoke starts drawing upward, you can build the fire normally
3. Use dry fuel only
Always use:
- Dry, seasoned wood
- Approved smokeless fuel (where appropriate)
Wet or poor-quality fuel makes cold plug problems worse.
What NOT to do
- ❌ Do not use flammable liquids
- ❌ Do not force a large fire immediately
- ❌ Do not ignore smoke entering the room
- ❌ Do not assume the problem will “clear itself”
When to call a professional
If cold plug issues happen frequently, it could indicate:
- A blocked or partially blocked flue
- Incorrect liner size
- Poor ventilation
- Chimney design issues
In these cases, the safest solution is a professional inspection.
We’re here to help
At Alfred Poppins, we don’t just sweep chimneys — we make sure they work safely and efficiently. If you’re experiencing repeated cold plug problems, we can inspect your flue, check airflow, and advise on the best long-term solution.
Contact Alfred Poppins for expert chimney sweeping, stove advice, and flue inspections.
