Airflow, Pressure and Temperature in Smoke Exhaust Fan Selection
Airflow alone is not enough to select a smoke exhaust fan. Pressure requirement, fire temperature, operating duration, duct resistance and installation conditions must be evaluated at the same operating point.
What does airflow determine?
Airflow defines the volume of air or smoke that must be moved over time. The required airflow should come from the project smoke-control calculation and design scenario.
Why does pressure matter?
The fan must overcome resistance from ducts, bends, dampers, silencers, grilles and other system components. Selecting only by airflow without the required total pressure can lead to the wrong fan.
How are temperature and duration evaluated?
The expected fire temperature and required operating duration should be checked against the fan performance class and supporting documentation.
Why can the operating point differ from catalog maximums?
Maximum airflow and maximum pressure figures are not a design point by themselves. The real operating point is evaluated where the fan curve and system resistance curve meet.
What information should be available for selection?
Airflow, total pressure, temperature class, duration, electrical supply, installation orientation, duct connection, environmental conditions and control method should be clarified as far as possible during selection.