Thailand's official AQI scale, the six pollutants behind it, the annual burning-season pattern, and why BAANLYY links to live official data instead of publishing its own real-time numbers — for every one of the 19 Thai cities BAANLYY currently covers.
The short version: BAANLYY does not publish live AQI or PM2.5 readings — those change hourly and only Thailand's own Air4Thai network can report them accurately in real time. What BAANLYY publishes instead is the framework: how the Thai AQI scale works, when and where the annual burning season hits hardest, and a direct link to the official live reading for every city we cover.
Thailand's Pollution Control Department (PCD) operates the Air4Thai monitoring network, which combines six pollutants — PM2.5, PM10, ozone, carbon monoxide, nitrogen dioxide and sulphur dioxide — into per-pollutant sub-index values, then reports the single worst-performing sub-index as that station's overall AQI. The result is grouped into five colour-coded bands:
| AQI range | Category | What it means |
|---|---|---|
| 0–25 | Excellent (green) | Air quality has no adverse impact on health or outdoor activity. |
| 26–50 | Satisfactory (light blue) | Air quality is acceptable; unusually sensitive individuals may notice minor effects. |
| 51–100 | Moderate (yellow) | Generally acceptable, though sensitive groups (children, elderly, those with respiratory or heart conditions) may experience mild effects. |
| 101–200 | Starting to affect health (orange) | The general public may begin to notice health effects; sensitive groups may experience more serious effects and should reduce prolonged outdoor exertion. |
| Over 200 | Affecting health (red) | Everyone may experience health effects; outdoor activity should be reduced or avoided, especially by sensitive groups. |
This is structured similarly to (but is not numerically identical to) the US EPA's 0–500 AQI — always read a Thai reading against the Thai bands above, and check Air4Thai directly (linked in Sources below) for the current figure at any specific station.
Thailand's air quality follows a predictable annual rhythm rather than being random. Roughly from late February through April, agricultural and forest burning across the region — combined with still air and temperature inversions that trap smoke in mountain valleys — drives PM2.5 to its highest levels of the year, typically peaking in March before monsoon rains from May onward clear the air. Northern Thailand is affected most severely: Chiang Mai and Chiang Rai in particular can see extended stretches of "unhealthy" or worse readings during this window, while Bangkok and Thailand's central and southern coastal cities generally see a much milder version of the same seasonal dip, or none at all in some years. BAANLYY's individual city Air Quality pages describe each city's own specific seasonal pattern rather than applying one nationwide description everywhere — a coastal or southern-island city's page will read very differently from a northern city's.
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General informational overview only — not medical, environmental or health advice. Air quality changes hourly; always check Air4Thai (Thailand's official real-time network) or another official source for the current reading before making health decisions, and consult a medical professional regarding any respiratory or health condition.
Primary and official sources are cited above. Government rules, fees and procedures in Thailand change over time and vary by office; always confirm current requirements with the relevant authority before relying on them. BAANLYY never takes paid placement in editorial content.