Bangkok, Thailand Air Quality & Smog

Dominant pollutants, when pollution and smog are worst, a notable historical episode, and the official monitoring agencies for Bangkok, Thailand — plus how to check the current reading. Bangkok reports air quality on the Thailand Air Quality Index, not the US AQI — our guide to world air-quality indices explains how the major scales compare.

Dominant pollutants

PM2.5.

Seasonal pattern: when smog is worst

Bangkok's problem season is the cool, dry months (roughly December–April), when stagnant air traps PM2.5 from heavy traffic and from agricultural and biomass burning across the region — including the northern provinces and neighbouring countries. The monsoon months are much cleaner. Thailand reports a 0–500 AQI similar in structure to the US scale.

A notable air-quality episode

Bangkok has faced recurring "PM2.5 season" crises — notably in 2019 and 2023 — with the city issuing health warnings, encouraging work-from-home, and at times closing schools as readings climbed into unhealthy ranges.

The local index and who runs it

Bangkok reports air quality using the Thailand Air Quality Index, not the US AQI — so the same air can read as a different number than you may be used to. The PCD publishes readings and the AQI through its Air4Thai service; see our world air-quality indices guide for how Thailand's scale compares.

• Thailand Pollution Control Department (PCD)

How to check air quality in Bangkok

For the official live reading, the agency portals above are the canonical source. To understand what the numbers mean, see our guide to world air-quality indices and how they compare to the US AQI. Smog Report puts glanceable air quality on your iPhone — widgets, Live Activities, Siri, and Apple Watch — free and with no account.

Common questions about Bangkok air quality

Why does Bangkok have air-quality and smog problems?

Bangkok's problem season is the cool, dry months (roughly December–April), when stagnant air traps PM2.5 from heavy traffic and from agricultural and biomass burning across the region — including the northern provinces and neighbouring countries. The monsoon months are much cleaner. Thailand reports a 0–500 AQI similar in structure to the US scale.

What are the main air pollutants in Bangkok?

Bangkok's dominant pollutants are PM2.5. The reading on any given day is usually driven by whichever of these is highest.

Has Bangkok had a major air-quality or smog event?

Bangkok has faced recurring "PM2.5 season" crises — notably in 2019 and 2023 — with the city issuing health warnings, encouraging work-from-home, and at times closing schools as readings climbed into unhealthy ranges.

What air-quality index does Bangkok use?

Bangkok reports air quality on the Thailand Air Quality Index (AQI), not the US AQI — so the same air can read as a different number than you may be used to. For live, glanceable readings on your iPhone, the free Smog Report app auto-selects the right local index for wherever you are.

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