Recently, Ghim and Son (1993) compared the air quality impacts of two point sources P1 and P3 in Seoul in the first quarter of 1988, whose emission rates were 99.9g/s and 49.4g/s, and whose stack heights were 75m and 21m. They said that higher concentrations from P3 in the nearby area were responsible for shorter stack height of P3. But concentrations were not raised so high only because the stack height was reduced from 75m to 21m. Volume of exit gas from P3 was also much smaller than that from P1.