Inches of water column were directly demonstrated by the last door to door vacuum sales pitch I saw, as a measure of suction. CFM are a perfectly comparable me

Inches of water column were directly demonstrated by the last door to door vacuum sales pitch I saw, as a measure of suction. CFM are a perfectly comparable measure of airflow. And an abstract "cleaning power" could be defined for various surfaces by putting a standardized dirt load on the surface and weighing what percentage remains after a standardized sweep.