Wasp nest in the chimney — what to do?
By Wespenprofis.ch · Reviewed by:Fachbewilligung Schädlingsbekämpfung VFB-S · Updated: 3 July 2026
At a glance
A wasp nest in a chimney or flue pipe usually sits deep inside the shaft and is not visible from the outside. Never light the fire to drive the insects out, and do not seal off the chimney outlet. Have the shaft assessed by a professional.
Why this situation is tricky
A chimney or flue pipe offers wasps a dark, sheltered cavity that is rarely disturbed — ideal conditions for a nest that often sits several metres down the shaft and is barely visible from outside. Things become problematic as soon as you want to use the fireplace again: smoke and heat do not reliably drive the insects outdoors, but rather into your living space, while burning nest material can impair the draught and create a fire risk. Even outside the heating season a nest in the chimney shaft is delicate, because the only escape route for startled insects often leads straight into the living space. In late summer, when the colony reaches its maximum size and irritability, this risk becomes more acute.
What to do straight away
- Never light the fire to drive the insects out.
- Keep the stove door or damper to the living space closed.
- Do not seal or cover the chimney outlet on the roof.
- If individual wasps get indoors, open the windows and let them fly out by themselves rather than swatting them.
- Call in a professional (/wespennest-entfernen) to assess the shaft properly and remove the nest.
Good to know
Depending on the depth and accessibility of the shaft, cold treatment or the targeted use of a biocide via the chimney outlet may be an option; mechanical extraction is rarely possible with a nest deep inside the pipe. After treatment the old nest is never recolonised, but a check of the shaft by the professional or the chimney sweep is still worthwhile before the next heating season. If the nest sits in the roof cavity rather than in the flue pipe, take a look at our guide on wasp nests in the roof. For the basics on how to proceed when you find a nest, see wasp nest found — what to do.
Frequently asked questions
Can I drive the nest out by lighting a fire in the fireplace?
No, that is dangerous and ineffective. Smoke and heat tend to push the insects into your living space rather than outside, and burning nest material can block the chimney and increase the risk of a fire.
How do I spot a nest in the chimney if I cannot see it?
Usually you notice a humming sound inside the chimney shaft, or you can see wasps flying in and out at the chimney outlet on the roof. The odd insect indoors can also be a sign.
Can the fireplace be used normally again after the removal?
As a rule, yes. Once the nest has been removed professionally it is never recolonised, but it is sensible to have a professional check whether the shaft needs cleaning.