This Standard provides a consistent, uniform methodology for evaluating the airtightness of building envelopes and heating and cooling air ducts, and the airflows of mechanical ventilation systems. These test procedures can be used as building diagnostics, in quality assurance and control, for determining compliance with codes and standards, and to determine input to energy simulations and ratings. The Standard recognizes some test procedures are easier to perform depending on house and HVAC system characteristics, and different codes and standards have specific testing requirements. Therefore, the Standard presents several alternative approaches for each measurement to allow flexibility in application of the standard.