The physical appearance of the samples was normal and black in color, and they appeared to contain much more material than what we have experienced in Hong Kong for the past 5 years.
The wind speed was low (0.9-1.9ms~1) and the wind direction was variable. This is not a favorable condition for the dispersion of air pollutants. The API (Air Pollution Index) was high at 105-168 except for SIRIM on 2 September