The purpose of this document is to prescribe unified test procedures and conditions for the experimental determination of mechanical energy loss coefficients for ductwork components, such as ducts, elbows, diffusors, and converging and diverging junctions. This document is a part of series of standards for ductwork used for ventilation and air conditioning of buildings for human occupancy. The position of this standard in the whole field of the standards for the mechanical building services is illustrated in the document. No existing European Standard is superseded. This document is available in English.