The U.S. Environmental Protection Agency 0030, the Volatile Organic Sampling Train (VOST), is used to determine the destruction and removal efficiencies of volatile organic emissions from industrial boilers co-firing hazardous waste. Previous reports detailing hysteresis effect for volatile organic compounds (VOCs), resulting from soot build-up on the interior surfaces of boilers and industrial furnaces, raised concerns of possible VOST measurement biases due to soot deposits within the VOST. This possiblity required laboratory investigation of the method under sooty conditions. Statistical evaluation of the data collected indicated that recoveries for two of the higher boiling VOCs (chlorobenzene and octane) appeared to be negatively influenced by the presence of soot on previously collected hazardous waste incinerator data, since the VOST-Soot effect was determined at moderately high soot loadings, which are atypical of properly operating hazardous waste incinerators.