Animals in the chimney

What moves in

An uncapped flue is a tree-trunk substitute. Birds nest in spring, squirrels move in year-round, and raccoons take the occasional winter den. The blockage shows up as a draft problem or scratching sounds.

Why it matters

A nest or animal blocks the flue the same way a clog does, and a blocked flue pushes smoke and carbon monoxide back into the house. It is a venting safety issue before it is a pest issue.

Removal and prevention

The animal comes out through the top or by coaxing down to the damper. The nest material clears, and a screened cap goes on after. Removal without the cap is an invitation for the next occupant.