Your lawyers since 1722

Improving Air Quality in High Density Cities

People living in high-density cities suffer from exposure to poor air quality and impacts on short and long-term human health continues to be a major concern. However, Hong Kong is making gradual progress towards improving its air quality and people’s health through various policies, cross-border initiatives and technology innovations. The retrofit of existing buildings will also contribute to indoor and outdoor air quality improvements in the long term.

Hong Kong faces two main air pollution issues. The first is local street level pollution and the second is regional smog. Commercial vehicles are the main source of street level pollution while smog is caused by a combination of pollutants from motor vehicles, marine vessels, industry and power plants in both Hong Kong and the Pearl River Delta (PRD) region. Hong Kong has implemented a number of measures to tackle these sources under its clean air plan. They include:

Vehicle emission control measures

  • An incentive-come-regulatory programme phasing out 80,000 diesel commercial vehicles and adoption of tighter vehicle emission standards amongst other measures
  • A Pilot Green Transport Fund to subsidize the testing of green innovative technologies relevant to the public transport sector and goods vehicles

Measures to reduce emissions from vessels

  • Working jointly with the Mainland to implement marine emission control for the domestic emission control area (DECA) along the Mainland’s coastal waters
  • Mandating vessels to switch to using compliant fuel while sailing or berthing

Reducing emissions from industrial sources and power plants

  • Requiring all commercial and industrial processes to use ultra-low sulphur diesel
  • Retrofitting and controlling emissions from existing power plants with the shift away from coal and requiring new power plants to use cleaner fuel such as natural gas
  • Incentivizing the two main local power companies to promote the development of renewable energy for generating electricity

Tackling regional air pollution problem

  • Hong Kong and Guangdong governments working jointly to reduce total emissions and improve air quality for the whole region—include retrofitting power plants, phasing out highly polluting industrial plants and introducing cleaner motor vehicles and fuels

According to air quality monitoring results from the PRD Regional Air Quality Monitoring Network, the average annual concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2) and respirable suspended particulates (RSP) in the PRD Region decreased by 81%, 28% and 36% respectively in 2018 compared to 2006 figures when the Network started to operate. While there is still some way to go to meet air quality goals as set by the World Health Organization, concentrations of all pollutants in Hong Kong, with the exception of ozone, have decreased in recent years.


Figure 1: Level of air pollutants in Hong Kong decreasing but with ozone at highest in the past 4 years


The HKSAR government will introduce further measures to reduce air pollutant emissions including electric ferries, electric public light buses, franchised bus low emission zones and installation of electric vehicle charging-enabling infrastructure.

Using technology to reduce personal exposure and health risk from outdoor air pollution

Equally important to improving air quality is to empower actions from citizens to improve their health. A new app was launched in June 2019 that aims to help users reduce their exposure to outdoor air pollution. Developed by the Institute for the Environment at the Hong Kong University of Science and Technology (HKUST), PRAISE-HK (Personalized Real-time Air-quality Informatics System for Exposure–Hong Kong) uses the Air Quality Health Index (AQHI) developed by the Hong Kong Environmental Protection Department to report current air quality and forecast air quality for the next 48 hours based on weather and pollution data modeling.

Figure 2: The PRAISE-HK App interface

Air quality can vary widely from one street to another in dense urban cities like Hong Kong due to differences in traffic and ventilation conditions. PRAISE-HK allows users access to real-time fine scale street-to-street variations in air quality information (down to 2-20 meters), and health risk information, so the user may make more informed decisions concerning his/her daily outdoor activities. In 2020, the app will integrate personal exposure tracking from outdoor to indoor environments and users will receive personal health recommendations based on their visited locations and health data.

To find more information on PRAISE-HK, click here

Retrofitting to Improve Indoor and Outdoor Air Quality in Commercial Buildings

Electricity generation is a major source of air pollution in Hong Kong and buildings consume 90% of the electricity generated. There is huge potential to retrofit some 42,000+ existing buildings to reduce energy consumption whilst providing a healthy indoor environment for occupants.

A recent study undertaken by the Institute for the Environment at HKUST examined the energy consumption and indoor environment in a real-case commercial office building with a retrofitted heating, ventilation, and air-conditioning (HVAC) system. Retrofitted measures included a sensor-based building management system, dehumidification of outdoor air, and a two-stage particle filtration system. Energy data was collected before and after the retrofit, field measurements were conducted in winter and summer to evaluate the thermal comfort and indoor exposure to air pollutants in the retrofitted area, and an experiment was designed to assess the benefits of upgraded filters on exposure to ambient particles during summer.

Key results of the study were:

  • The retrofitted HVAC system reduced energy use by 50% while maintaining an acceptable indoor thermal environment
  • For majority of the time, indoor particle levels complied with World Health Organization guidelines
  • The upgraded filtration system with a pleated filter reduced outdoor PM ingress by 30%-60% more than the aluminium filter used prior the retrofit
  • Fine particles level was found to be reduced by 70% at the exhaust location which flowed through the retrofitted HVAC system and was expelled to the outdoors leading to improvements to outdoor air quality

The study demonstrated co-benefits of energy savings, better indoor air quality, maintaining occupants’ thermal comfort and enhancing productivity. The retrofit of more existing buildings in Hong Kong can collectively serve as a purification system to improve ambient air quality and generate wider health benefits for the community.

To find more information on the study, click here

Ir Dr Cary Chan, JP is the Executive Director of the Hong Kong Green Building Council
Dr Margaret Kam is Manager – Sustainable Built Environment at the Hong Kong Green Building Council