Abstract This study considered many wind tunnel experiments using isothermal heavy gas and cryogenic gas of the same specific gravity as LNG, and compared the results of time-averaged concentration with those of field experiments, such as the Thorney Island Experiments (1987) and the China Lake Experiments (1987). The laboratory and field measurements agreed well, which suggests that a wind tunnel experiment can simulate important aspects of the diffusion of a cryogenic gas like LNG. These wind tunnel data were also compared with two well-known calculation models, DEGADIS and FEM3. We measured the fluctuation of concentrations for two cases with and without a building, and compared the standard deviation of concentration fluctuation with results calculated by our original numerical code of standard deviation (STD) model. The experimental and numerical results agreed well for unobstructed flows, but there were some discrepancies when a building was present. In addition to the comparison of the standard deviation of the concentration fluctuations, we compared the probability density function (PDF) produced by wind tunnel results with that predicted by a direct numerical simulation (DNS).