In this study, UV irradiation reactors were used to eliminate 4 types of volatile organic compounds (VOCs) in various experimental conditions. The 4 types of VOCs used include acetone (AC), chlorobenzene (CB), dichloromethane (DCM) and methylbenzene (MB). An ozone producing low-pressure mercury lamp that emits UV irradiance at 254 nm and 185 nm was used. The tested operating conditions included UV light intensity, inlet VOCs concentrations, empty bed retention time (EBRT), background gas and relative humidity (RH) of the gas. Firstly, higher UV light intensity is confirmed to have higher VOCs removal efficiency (RE). Higher inlet VOCs concentration will result in lower VOCs RE, and the decreasing trends of different VOCs are not identical. At the same inlet VOCs concentrations, increasing the EBRT will result in a rise in VOCs RE, but a further increase in EBRT will bring about less enhancement in RE. Moreover, UV irradiation in oxygen has the highest VOCs RE compared with that in air and nitrogen gas (N2), indicating that photolysis and photooxidation are both important. Finally, there was no increase the VOCs RE at the increase in RH. All the experimental results indicate that an identical set of operating conditions should be applied when the removal capacities of different VOCs according to the UV irradiation amount are compared. Keywords : EBRT, Relative humidity, UV irradiation, Volatile organic compounds (VOCs)