The Department of Environment has advised the public to refer to its official Air Pollutant Index Management System (Apims) for data on air quality as those from third-party sites may not be accurate.

For example, it said the Air Quality Index (AQI) used by the AirVisual portal only relies on censors and therefore the reading "is seen as inaccurate compared to the DOE's Air Pollutant Index (API).

It said the DOE's API also measures particle matter of up to 2.5 microns (PM2.5).

"The usage of PM2.5 in the calculation of API is in line with international standards used by many countries," the department said in a statement today.

The DOE said the IPU data is the official one for the country and has been verified before it is disseminated.

"Referring to the API provided by other portals other than the JAS could cause confusion and give an inaccurate picture.

"The public is advised to only refer to the official reading issued by the DOE," said the statement.