A restriction can come from deposits, nests, debris or damaged components. Removal is only part of the job if the flue itself has deteriorated.
Published by Chimney Sweep Pages · September 24, 2026 · Editorial method
First decision
Stop using the connected appliance until the vent is assessed.
Possible explanations—not a diagnosis
Fallen liner or masonry fragments
Nesting material and outdoor debris
Heavy deposits or a damaged termination
Several conditions can occur together. Only an appropriate on-site assessment can distinguish them in your home.
What the investigation should clarify
A professional may need camera access and appropriate cleaning equipment to identify the obstruction and its source. Ask what will happen if access is limited or material indicates liner damage. A clear passage alone does not establish the condition of the rest of the system.
Do not push rods into an unknown obstruction or light a fire to see whether smoke escapes.
One question worth asking
Will the report identify both the obstruction and the condition of the vent after removal?
Ask for the findings, access limitations and proposed next steps in writing. Keep diagnosis separate from a repair estimate so you can seek another opinion with the same evidence.