Most people do not understand what static pressure and airflow specifications are;
Static pressure (mm H2\o0 is the maximum height the fan can push water up the tube before air stops moving. Static = stopped. the weight of water in the tube is the difference in the pressure the fan is pushing compared to pressureon the air everywhere else around it.
Cubic Feet per Minute (cfm) is how much air the fan can move in open space with nothing in front or behind it.