The symptom
The fire starts normally, but smoke spills when a large exhaust fan is switched on.
How to reason without overreaching
- The repeatable fan connection makes house pressure relevant.
- Blockage, flue condition, fuel and geometry still require assessment.
- Opening a window may reveal a pressure relationship but is not a permanent diagnosis or repair.
Reasonable next steps
- Stop use when smoke enters the room.
- Record which fans and doors affect the symptom.
- Request a draft assessment that considers the house and chimney together.
Actual property conditions may change every conclusion. For immediate danger, leave the affected area and call emergency services.
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