Air Quality Monitoring Stations in Hong Kong

The territory of Hong Kong can be broadly classified as industrial, urban and new development zones according to the major land use in the most populated areas of the zone.

Air Pollution Index

M.M YEUNG AND S.W. PANG

    Not too long ago, most people in Hong Kong had never heard of an air pollution index. Some might have heard or seen the report of such an index but only when they were travelling or living in foreign cities. Recently, a survey done by the Social Research Centre of the University of Hong Kong found that almost everyone in Hong Kong knows that an air pollution index is published daily by the Environmental Protection Department. About 60% of the people consider that the index is useful to them.

The first air pollution index was published in Hong Kong by the Environmental Protection Department on 6 June 1995. Since then, an index has been released everyday at 4:00 p.m., except on Sundays and holidays, and reported by television, radio and most of the newspapers. People can also find out the index by calling 2827 8541. Very quickly, listening to the broadcast of the air pollution index has become part of the normal life of many people.

The Environmental Protection Department operates a network of monitoring stations to measure air pollution. The network is designed and operated to meet the highest international standards in measuring air pollution. It is certified by the Hong Kong Laboratory Accreditation Scheme and has been highly approved by experts from overseas countries and the United Nation's Environmental Programme.

Measurement data are sent back to a computer located in Wanchai via telephone line. There are a number of chemicals existing in the atmosphere, with different characteristics and at different concentrations. While the department can fully understand these data and make plans and proposals based on them, a person without much science background might find it difficult to understand these measurement data if they are presented in their original form. In view of this, it is better if these raw measurement data can be transformed to a single number to help the general public understand easily whether the air is good or bad.

To achieve this goal, the Hong Kong Jockey Club donated money to fund a survey of air pollution index systems in use in other parts of the world, and a study to develop a system for Hong Kong. The system now in use is modelled on the Pollution Standard Index used in the United States. Very similar systems are being used in cities in Australia, Taiwan, Singapore and other countries.

The Air Pollution Index increases as the air quality degrades. As the index exceeds 100, the most vulnerable group will begin feeling discomfort and , more people will be less able to take exercise as the index increases further.


The system transforms all air pollution measurement data into a number between 0 and 500. An index value between 0 and 50 means that the air quality is good. An index value between 50 and 100 means that the air is moderately polluted. When the index value is over 100, one or more air pollutants have already breached the limit allowed in Hong Kong air quality objectives. People more susceptible to air pollution, such as those who have heart or respiratory diseases, are advised to reduce physical exertion and outdoor activities as far as possible. When the index value is over 200, which have not occurred in Hong Kong since the system was launched in June 1995, the air pollution will be so high that all people are advised to reduce physical exertion and outdoor activities as far as possible.

To serve the community better, we will expand the network by adding a monitoring station in the Eastern District. Additionally we will add two roadside monitoring stations to the network, to assess the pollution levels on busy road. Subsequently a record index representing the air quality in busy streets will be introduced.


Which months have good air quality conditions?

Back to Chapter 3 Menu