Analysis of concentration fluctuations in gas dispersion around high-rise building for different incident wind directions

► We examine unsteady characteristics of cross-contamination in high-rise building. ► The values of concentration fluctuation intensity were greater than 1 and can be up to 10. ► The intermittency factor and peak-to-mean ratio can be up to 0.8 and 70, respectively. ► The concentration fluctuation is increased under open-window conditions. ► Instantaneous peak infection risk is below 0.1% under open-window condition.