Frequently Asked Questions

API stands for "Air Pollutant Index". It is an index developed that closely follows the United States Environmental Protection Agency (USEPA) Pollution Standards Index in providing easily comprehensible information about the air pollution level.

The API value gives an indication of the air quality as shown:


Low pollution without any bad effect on health

Below 50

Moderate pollution that does not pose any bad effect on health

51 - 100

Worsen the health condition of high risk people who is the people with heart and lung complications

101 - 200

Worsen the health condition and low tolerance of physical exercises to people with heart and lung complications. Affect public health

201 - 300

Hazardous to high risk people and public health

More than 300

API system includes 6 major air pollutants which could cause potential harm to human health should they reach unhealthy levels. The air pollutants included in Malaysia's API are ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2), particulate matter with a diameter of less than 2.5 micron (PM2.5) and particulate matter with a diameter of less than 10 micron (PM10).

At present, we cannot forecast the API readings, but we are working closely with other countries in the sub-region under the Regional Haze Training Network programmes on this matter.

Yes, it is possible to predict the pattern or the severity of the haze using appropriate modeling software which includes weather and atmospheric data such as wind speed, prevailing wind and air mass concentration.

Ozone is one of the 6 major pollutants in the API readings. Normally the ozone concentration will be high in the afternoon due the presence of sunlight and Volatile Organic Compounds (VOCs). Normally, areas with high traffic volume recorded high ozone concentrations due to emissions from the exhaust of motor vehicles.

Yes, it requires a written application from interested parties. Application for the data can be addressed to the Director of Air Division of DOE, Putrajaya.

For now, there are only 65 monitoring stations throughout Malaysia. However, the Department is exploring alternatives on mobile equipment to wider the coverage. So for now, these 65 stations are sufficient enough for the public to know the API readings at their respective states and places near them.

For now, hourly API readings are published to the public so they will be well informed and prepare themselves if the air quality worsens. To view the API readings, the public can go to the DOE website at

The Malaysian Air Quality Guidelines (MAAGs) which form the basis for calculating the API are presented in Table 1. These guidelines have been derived from available scientific and human health data, and basically represent "safe levels" below which no adverse health effects have been observed. The MAAGs are generally comparable to the corresponding air quality standards recommended by the World Health Organization and other countries.

The averaging time, which varies from 1 to 24 hours for the different air pollutants in MAAGs, represents the period of time over which measurements is monitored and reported for the assessment of human health impacts of specific air pollutants. As such, the air pollution indices are normally monitored and reported for the same averaging times as those employed for the air quality standards/guidelines.

The API values are reported for varying averaging time as follows:

  1. a) PM2.5 and PM10 on 24-hour running averages.
  2. b) CO and O3 on 8-hour running averages.
  3. c) SO2 and NO2 on 1-hour running averages.

The API for PM2.5 reflects specifically levels of particulate matter with a diameter of less than 2.5 micron pollution and it may not be linked directly to visibility factors, as visibility is often determined by results of semi-quantitative observations over relatively shorter time periods.

The API value reported for a given time period represents the highest API value among all the sub-APIs calculated during that particular time period. The predominant parameter contributing towards a particular API value is normally indicated alongside the API value. This approach is an effort to promote a uniform and comparable API system. Ideally, all sub-API values exceeding the API 100 threshold limit should also be reported in addition to the predominant API value per se.

To determine the API for a given time period, the sub-index values (sub-API) for all 6 air pollutants included in the API system are first calculated using the above mentioned sub-index functions for the air quality data collected from the Continuous Air Quality Monitoring Stations (CAQMs). The corresponding air quality data are subjected to the necessary quality control processes and quality assurance procedures, prior to the sub-index calculations.

Table 1: Malaysia Air Quality Guidelines, Adopted in Air Pollution Index Calculation.
(ppm) (μg/m3)
OZONE 1 HOUR 0.10 200
8 HOUR 0.06 120
8 HOUR 9 10
8 HOUR 0.04 75
1 HOUR 0.13 350
24 HOUR 0.04 105
PM10 24 HOUR   150
1 YEAR   50
# μg/m3