What needs to be clarified
Measure airflow and its dependence on door position, distinguishing fan performance, duct resistance and room air supply under the operating conditions examined.
Materials to prepare
- Ventilation design, fan specifications and duct plan
- Door replacement and air-inlet information
- Grille access and a log of other fans' operation
What to compare
Measure flow under comparable conditions with the door open and closed; record pressure differences and accessible air paths. Inspect grille, backdraft damper and accessible duct sections, comparing settings with specifications. Record other extractors, window positions and weather for each series.
Possible outcome of the analysis
Mode-specific airflow results and an air-path diagram may identify supported restrictions; recommendations reflect measured conditions and note any need to inspect concealed ductwork.
Limits of the conclusions
Motor noise and paper movement do not replace airflow measurements. One reading with an open window cannot describe every mode or establish concealed duct condition.