This proposed standard provides a laboratory test method for assessing the performance of air cleaning devices used in gas-phase air cleaning systems. The test method is for filters and complete devices designed to be used for in-duct gaseous contaminant air cleaning in their commercial form at full-scale. These gaseous contaminant air cleaning devices are those most often selected for use in building HVAC systems.The results can provide useful information for the design and selection of air cleaning systems for controlling indoor concentrations of gaseous air contaminants.