The purpose of leak testing buildings is to prevent the waste of energy used to maintain building comfort. In spite of what some here seem to think there are established parameters for leakage. Total allowable leakage is determined by the pressure the building is tested. Allowable leakage at that pressure is specified per square foot of external building surface. The last building I tested was a commercial building. The allowable leakage at CFM50 was 0.15 CFM per square foot of external surface. The total external area was around 500,000 sq ft. For this building I converted the CFM50 requirements to 0.05 in wg and tested at 0.05 inch. That gave the engineer the allowable leakage and the actual leakage at operating conditions.
The statement on another thread that a few hundred CFM doesn't matter is wrong. If tested at CFM50 and 400 CFM of bogus airflow is present that represents about 100 CFM @ 0.02 inch wg and at 95F@45%RH is 6600 BTUH (1/2 ton) of cooling. Blower doors are a convenient method of getting fairly close to building leakage if properly done and should be limited to small structures. Measuring outside airflow in commercial buildings can be very accurate if done by a TAB person that knows how. Houses are not that easy which makes blower doors useful. Commercial building outside air flows can be measured by pitot traverse but houses seldom can be.
The assumption that an air conditioning unit moves 400 or 500 CFM per ton doesn't work for conditioning outside air. With 95F@45%RH it only takes 200 CFM per ton.
Vents to the outdoors need to be blocked off if necessary to only include leakage of the dampers if and as applicable.