This standard is for field application in both new and existing buildings. This standard can be applied to determine whole-system or sectional leakage airflow. This standard provides a. test procedures and requirements for measuring inlet and outlet airflows during system operation@ b. methods for calculating leakage airflows to/from system surroundings@ c. methods for calculating leakage test uncertainties@ d. methods for documenting the test plan@ and e. methods for reporting test results. The test procedures in this standard are limited to singleduct supply and independent exhaust air systems. This standard is not for determining return air leakage. This standard is not for determining leakage involving ceiling and floor plenums@ systems serving pressure-controlled spaces@ or air dispersion systems. This standard does not replace ductwork pressurization leakage testing. This standard does not specify leakage acceptance criteria. This standard shall not be used to override any safety@ health@ or critical process requirements. PURPOSE This standard specifies a method of test to determine leakage airflow and fractional leakage of operating HVAC air distribution systems and determines the uncertainty of the test results.