Before any check
Photograph Supply and return imbalance, record the trigger and preserve the original condition. Confirm that access is safe and that the check will not disturb electrical equipment, hazardous materials, structural support or contaminated water.
Check the trigger
Repeat only one ordinary operating or weather-linked variable where safe. For this facet, the useful question is whether How delivered supply air and available return paths can pressurize one room while depressurizing another. changes in a predictable way when that variable changes.
Check the route
Inspect accessible transitions through bedroom, closed room, stairwell, mechanical zone, return-air path or exterior boundary without cutting, drilling, removing guards or opening energized or regulated assemblies. Note both positive clues and intact boundaries.
Use a reference condition
Compare an unaffected room, component, time period or weather event using the same method. A control prevents normal variation from being mistaken for evidence of failure.
Record the result so it can be repeated
- Compare door-open and door-closed conditions
- Log exhaust fan, heating and cooling cycles
- Use tissue or smoke only where safe and never near combustion or detectors
- Use the same camera position, scale and measurement location.
- Write down what would count as no change before beginning the check.
Stop boundary
Combustion backdraft concerns, carbon monoxide alarms, strong fuel odor or unsafe electrical equipment require immediate safety action rather than airflow experiments. The source set for this guide includes 4 official records selected for this path. They provide general technical and safety context; they do not determine the condition of a particular house.
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.
