The author calculated the frequency of high concentration of sulfur dioxide (over 0.2 p. p. m.) in one hour according to wind direction, wind velocity and Pasquill's stability, and the author also calculated the average concentration of sulfur dioxide according to wind direction and velocity. The results obtained were as follows; 1. S, SSW, SW, and WSW winds (mainly sea breeze) bring the air pollutant to the northern part in Mizushima Industrial Area. Wind direction and wind velocity that brings. a higher concentration of sulfur dioxide to Fukuda-cho, Minami Kasuga-cho, and Amagi were S, SW, and SSW winds of 3～4 M/sec. In Mizushima Harbour Office, high sulfur dioxide concentartions were measured in S, SW, 2～3 M/sec. and SW, 2～5 M/sec. Average sulfur dioxide concentrations were higher in S, SW, 2～4 M/sec. in Fukuda-cho, Minami Kasuga-cho and higher in SSE 6 M/sec., SSW 6～7 M/sec., SW 2～5 M/sec., and S 3 M/sec. in Mizushima Harbour Office. 2. Unstable sea breeze brings higher concentrations of sulfur dioxide to Fukuda-cho and more stable sea breeze brings higher concentrations to Amagi.
From the calculations of diffusion by Pasquill's chart it was shown that the diffusion in C-stability brings high concentrations of sulfur dioxide to Fukuda-cho, and the diffusion in D-stability brings to Amagi.