Air duct system fan (fan, wind pressure, into the air filter resistance) how?

Air duct system fan air volume is generally measured by the maximum filter airflow 1.3 times the calculation; duct resistance is generally calculated according to 1.2 times the resistance calculation, inlet air filter resistance is calculated according to the initial resistance of 2 times; The rated air volume and wind speed of the tested filter must be such as to ensure the leakage of the tested filter installation frame. Otherwise, the accuracy of the data will be affected.