Tuen Mun’s general air-quality monitoring station recorded an Air Quality Health Index of 10+, classified as severe, at 5pm on October 13, according to the Environmental Protection Department’s index information.
At the same time, North, Yuen Long and Sha Tin had very high readings, above 8. Nine districts, including Central and Western, Southern, Eastern and Kwun Tong, recorded readings of 7, classed as high.
When the health-risk level is very high or severe, the department advises children, older people and people with heart or respiratory illnesses to reduce or avoid physical exertion and outdoor activities. Other members of the public should limit outdoor exertion and time outside, particularly near busy traffic. Employers should assess risks to outdoor workers and take suitable precautions.
The department said weak winds hindered the dispersal of pollutants, while strong sunshine encouraged photochemical smog and the rapid formation of ozone and fine particulates across the Pearl River Delta. The Hong Kong Observatory forecast an easterly airflow later on October 14, and the department expected air quality to improve then.