Chlorine dioxide (ClO2) gas is a powerful oxidizing agent in many industrial applications for food processing, drinking water and cleaning treatments. It is considered for use in an increasing number of fresh food applications over a wide range of temperature and pH conditions due to its sanitizing capability. During the disinfectant treatment in a closed chamber or packaging system, ClO2 gas is typically exposed to environmental factors such as light, temperature, and humidity which influence its disinfectant efficiency. Determining ClO2 gas reaction rates and mass transfer properties are extremely important for the design of proper sanitization treatments. The aim of this work was to determine the diffusion coefficient for ClO2 gas in air and reaction rates under dark, UV-A and fluorescent lamp exposure. The effect of temperature on the diffusion of ClO2 was also assessed. A system was designed to measure these properties. The diffusion coefficient was found to be 0.129, 0.145, 0.173 cm(2) s(-1) at 5, 23, and 40 degrees C, respectively. Degradation of ClO2 gas under dark, UV-A and fluorescent lamp exposure was found to follow a first-order reaction. Degradation using a 40 W UV-A lamp was approximately four orders of magnitude larger than with a 34 W fluorescent lamp. A methodology is proposed for quantifying the amount of ClO2 gas needed in a package and/or treatment chamber. (C) 2014 Elsevier Ltd. All rights reserved.