Possible causes, not a remote diagnosis
The investigator may consider deposit accumulation, obstructions, chimney configuration, appliance compatibility and house pressure. A recent remodel or replacement window installation can be useful context without proving causation.
What to document safely
Record when the trouble began and any changes to the appliance or home. Describe weather and fan use from memory. Do not light test fires to collect data.
Keep the appliance model, fuel, previous report and date of last service together. A clear sequence of events can be more useful than deciding in advance which component must be replaced.
Your next service conversation
Ask for a draft assessment that distinguishes confirmed faults from proposed explanations. If smoke spills indoors, stop using the system and follow the smoke guidance.
Smoke and draft investigations →Will a different cap fix poor draft?
Possibly in some assessed situations, but a cap should not be selected on guesswork. Ask what evidence supports the change and how the result will be evaluated.
Ask for evidence before approving repairs
Request a report that distinguishes what was observed from what remains uncertain. Ask the company to identify any area it could not inspect and whether another trade is needed. If a major repair is proposed, compare a second written scope using the same appliance details and findings.
Do not treat a directory profile, an estimate or this page as clearance to use an appliance. Ask the attending professional what must be resolved before reuse.
Read the detailed guide and its sourcesTake the service question to your location
Use the local guide to prepare questions about access, building history and the authority responsible for your address. The service brief is national guidance; local permits and current burn restrictions must be checked separately.