Clean Air Schools for Hong Kong: Air Quality Insights from May to Jul 2023

“Clean Air Schools for Hong Kong” was co-organized by Clean Air Network (CAN) and Institute for the Environment of the Hong Kong University of Science and Technology (IENV HKUST), aimed at helping the schools to get to know the air quality in their schools, and solving the problem from the source. We are monitoring the air quality in 8 schools from densely populated and highly trafficked Tuen Mun and Sham Shui Po district. The fourth quarterly report has been released and the insights are as below.


Cleaner wind blown from the ocean and closing the windows can block pollutants during typhoon


The outdoor air quality improved in this quarter, the concentrations of nearly all of the air pollutants decreased, and the drop in the particulate matter was related to the wind direction during summer. According to previous studies, summer in Hong Kong is mainly affected by southeast wind coming from the ocean, this can bring cleaner air to the territory, thus lowering the recorded concentration of particulate matter.


For the indoor air quality, as the local temperature was rising across the quarter, classrooms started turning on air-conditioners which could lead to accumulation of carbon dioxide. Therefore, a rise in the concentration of carbon dioxide in some classrooms was recorded. Moreover, when the Tropical Storm Talim hit Hong Kong, the team discovered that whether the windows and doors were closed could be affecting the indoor concentration of the particulate matter. So, to prevent the infiltration of air pollutants, the schools should ensure the windows and doors are closed before adverse weather.


Monsoon Wind Direction in Hong Kong
Graph 1: Monsoon Wind Direction in Hong Kong


Double ventilation system found to lower CO2 level from tests


Clean Air Schools for Hong Kong has been collecting data for over a year since August 2022, and to grant clean air in schools for students and teachers, the team has also started to take action. Ventilation tests were conducted in some schools. The team discovered that in most of the classrooms, compared to just turning on one or none of the exhaust fans or fresh air units, the carbon dioxide concentration significantly dropped when using both exhaust fans and / or fresh air units, indicating that good indoor ventilation could help to improve the indoor air quality, which lowers the chance of dozing, insufficient concentration, dizzy, and headache among students.