5.1 The procedures presented in this test method are available, in part, in Test Methods D3685/D3685M, as well as the ASME Methods (PTC 19.10-1968, PTC 19.10-1981, and PTC 38-1980) given in 2.3 and Footnote 5,⁵ the 40 CFR Part 60 given in 2.4, and the publication given in Footnote 6.⁶

1.1 This test method describes measurement of the average velocity of a gas stream for the purpose of determining gas flow in a stack, duct, or flue. Although technically complex, it is generally considered the most accurate and often the only practical test method for taking velocity measurements.

1.2 This test method is suitable for measuring gas velocities above 3 m/s (10 ft/s).

1.3 This test method provides procedures for determining stack gas composition and moisture content.

1.4 The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are for information only.

1.5 This test method is applicable to conditions where steady-state flow occurs, and for constant fluid conditions, where the direction of flow is normal to the face tube opening of the pitot tube employed in the method. The method cannot be used for direct measurement when cyclonic or swirling flow conditions are present.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.