Air Quality Index (AQI)

The U.S. Department of State and Environmental Protection Agency (EPA) are working to report air quality at Embassies and Consulates around the globe. As part of this initiative, U.S. Mission Thailand is reporting the U.S. EPA’s Air Quality Index (AQI) calculated from measurements of airborne fine particulate matter (commonly referred to as PM2.5 because they are less than or equal to 2.5 microns in diameter). These data are captured by monitors owned and maintained by the Royal Thai government. The U.S. AQI for Bangkok is calculated using data from monitor 50t located at the intersection of Rama IV and Ratchadamri roads. The U.S. AQI for Chiang Mai is calculated using data from monitor 36t on Prapokkloa Road in the old city area of Chiang Mai.

The air quality data collected from these monitors are translated into actionable information by the U.S. Environmental Protection Agency’s (EPA) NowCast algorithm. This algorithm converts raw PM2.5 readings into an air quality index (AQI) value that can help inform health-related decisions. The index is calculated based on hourly measurements collected over a three to twelve hour period depending on the variability of particulate concentration.

Thank you to the Royal Thai government for providing these data sources and allowing us to publish on this website.

U.S. Mission Thailand does not track other contaminants that contribute to air pollution [e.g. coarse dust particles (PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO)].

Current AQI Calculation: Bangkok

The U.S. EPA AQI value can help Americans in Thailand make health-related decisions:

Air Quality Index Levels of Health Concern Numerical Value Meaning
Good 0 to 50 Air quality is considered satisfactory, and air pollution poses little or no risk
Moderate 51 to 100 Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
Unhealthy for Sensitive Groups 101 to 150 Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Unhealthy 151 to 200 Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Very Unhealthy 201 to 300 Health warnings of emergency conditions. The entire population is more likely to be affected.
Hazardous 301 to 500 Health alert: everyone may experience more serious health effects.


  1. For the Royal Thai Government’s air pollution data and monitor locations, visit
  2. Thailand’s reported AQI is informed by multiple pollutants in Thailand. It does not directly correspond to the U.S. EPA AQI.
  3. Values above 500 are considered “Beyond the AQI.” Follow recommendations for the “Hazardous category.” Additional information on reducing exposure to extremely high levels of particle pollution is available here.