1. Stop at the safety boundary
Do not assume a larger fan will solve a blocked or disconnected duct.
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
Showering, fan operation and outdoor conditions.
4. Compare, do not assume
Supports this pathway
- Mirror and walls stay wet
- Fan airflow is weak
- Humidity remains elevated after the room is vacant
Weakens this pathway
- The room dries quickly with the door open
- Only one cold surface condenses
- A concealed leak keeps one area wet
5. Repeat only safe checks
- Track humidity before, during and after use
- Check airflow at the grille with tissue
- Confirm the fan terminates outdoors
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. A ventilation professional should measure airflow and inspect the full duct route.
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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