Air infiltration is the air which passes through the windows/doors and curtain wall from the exterior to the interior through gaskets, imperfect joinery between horizontal and vertical mullions, weep holes and imperfect sealing of the building. TTS performs valuable role in performing the air leak test for exterior windows/doors and curtain wall of various building as per ASTM E783. Air leakage index or air permeability of a building can be measured at site. The test can also be combined with visualization techniques to locate the air leakage paths.