This document explains CTM-041. This method may be applied when determining volumetric flow in rectangular stacks and ducts to account for velocity decay near the walls. Adherence to the requirements of this method will enhance the quality of the data obtained from air pollutant sampling methods. Return to Rectangular Duct Wall Effects for more information.

• Conditional Test Method (CTM-041)—Determination of Volumetric Gas Flow in Rectangular Ducts or Stacks Taking into Account Velocity Decay Near the Stack or Duct Walls (PDF)(17 pp, 242 K, January 8, 2003)