CFM50
CFM50 is the airflow (in cubic feet per minute) needed to depressurize a building to 50 Pascals during a blower-door test. It is the raw output from the blower door. CFM50 by itself is hard to compare across different home sizes, so it is usually converted to ACH50 (which normalizes against conditioned volume). A leaky 2,000 sq ft home might measure 2,500 CFM50; a Passive House of the same size targets under 200 CFM50.