1. Stop at the safety boundary
Do not perform deliberate backdraft tests or operate combustion appliances under unsafe conditions.
2. Capture the baseline
Take one context photo, one close view and a short note describing location, date, weather, recent water use, equipment state and occupancy.
3. Track the trigger
Kitchen hood, bath fans, dryer or HVAC operation.
4. Compare, do not assume
Supports this pathway
- Odor starts when fans run
- Opening a window reduces it
- The fireplace is unused but connected to outdoors
Weakens this pathway
- The smell occurs with no fan operation
- Smoke is actively spilling
- A separate drain or appliance is the source
5. Repeat only safe checks
- Stop fans if smoke or combustion gases enter
- Record which device triggers odor
- Use a carbon-monoxide alarm as required by local guidance
6. Decide the next step
If the pattern is active, expanding, safety-related or requires opening inaccessible construction, stop self-help testing and prepare an evidence-based handoff. Use a qualified chimney or combustion-safety professional.
7. Verify the outcome
After any action, repeat the same observation under a comparable trigger. A dry surface immediately after work is not sufficient proof when the original symptom was intermittent.
Observe→Compare triggers→Repair source→Verify outcome
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