Define the question before measuring
A tighter house still needs controlled replacement air when exhaust, combustion or occupancy removes or changes indoor air.
Capture a useful baseline
Record the exact location, date, current weather or equipment state, recent activities and the first visible, audible, sensory or measurable change. Keep one unaffected reference point.
Safe observations to repeat
- List simultaneous exhaust devices
- Check whether dedicated makeup air exists
- Request pressure and combustion-safety testing
Compare supporting and weakening evidence
Supports the pathway
- Pressure symptoms appear only under high exhaust
- Opening a safe exterior window changes the pattern
- Ventilation commissioning is absent or outdated
Weakens the pathway
- No exhaust source is operating
- The building is highly leaky everywhere
- The symptom is caused by a direct spill
Interpret the result conservatively
Look for a repeatable relationship between trigger, location, timing and change. Treat exceptions as useful evidence rather than forcing every event into one explanation.
Escalation boundary
Do not improvise permanent openings or disable alarms; makeup-air design must respect climate, fire and combustion safety.
Close the loop
If work is performed, repeat the same observation under a comparable trigger and through the original lag window. Record both recurrence and non-recurrence events.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
