The incidence of large-scale fires continues to rise, and the effects of radiation from these fires contributes to their continued spread. Water sprays have been widely used as an effective method to contain thermal radiation from fires. Results from previous studies on the sizes of water droplets in the spray barrier have limitations due to the significant computational time or complex analytical procedure involved. The aim of this study is to determine the optimal size of water droplets in the barrier mist using radiative transfer analysis for effective shielding of the radiation from the surroundings. The radiative properties of water droplets were analyzed using the Mie scattering theory and a radiative transfer analysis of the mist layer was performed. This demonstrated that the spectral reflectance of the mist layer can be controlled by the water droplet diameter. The effectiveness of optimizing the water droplet size in the mist layer to maximize protection from thermal radiation was also validated by experiments to evaluate the radiation shielding performance of the mist barrier. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.