Air tightness of the building enclosure is critical to modern building. Modern buildings need to meet more stringent air leakage standards. Engineers are using smaller allowances for air leaks in their HVAC systems. Testing larger buildings for air tightness requires multiple blower doors working in unison, in conjunction with guarded pressure zones, to measure the leakage rate of the building enclosure. TBS employs the latest technology, in combination with multiple blower doors, to measure the air leakage through the building enclosure, in accordance with ASTM E779 methodologies.