Standard 126 provides a standardized method of test to determine the strength and durability characteristics of HVAC ducts under various loading and environmental conditions. Standard 126 was written to address all duct shapes and materials and is unique among standards in comprehensively addressing a full range of structural and durability tests, including pressurizing ductwork, applying superimposed loads, dropping weighted implements for impact or puncture, applying tension to the duct, bending flexible duct 180 degrees, subjecting the ductwork to temperature and humidity changes, and bursting or collapsing the ductwork under pressure.

First published in 2000, Standard 126 is a joint project of ASHRAE and the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA).