What is the Air Pollution Index?

The Air Pollution Index (API) is a simple way of describing air pollution levels. In Hong Kong, the API converts air pollution data from several types of pollutants into a value ranging from 0 to 500. Similar systems are widely used in many other places such as the United States, Australia, England and Singapore.

Apart from reporting real-time hourly APIs, we also provide API forecast which serves to alert the public before the onset of serious air pollution episodes. It helps the general public, especially susceptible groups such as those with heart or respiratory illnesses, to consider taking precautionary measures when necessary.