Singapore Air Quality Index (AQI)
City-state · Southeast Asia · Peatland haze from Indonesia · PSI monitoring · 5.9M population
🔥 Haze Season: June–October
During the Southwest monsoon, smoke from Sumatra and Kalimantan peatland fires reaches Singapore in 12–36 hours. In bad years (2015, 2019), PSI reached 341 (Hazardous). In good years, it may stay below 100 all season.
Monthly AQI Trend — Singapore
NE monsoon (Nov–Mar): cleanest · SW monsoon haze season (Jun–Oct): elevated and volatile — spike to 200+ possible in severe years
PSI vs AQI: Singapore's Index Explained
| Index Level | PSI Category (NEA) | AQI Category (US EPA) | PM2.5 Equivalent |
|---|---|---|---|
| 0–50 | Good | Good | 0–12 μg/m³ |
| 51–100 | Moderate | Moderate | 12–35 μg/m³ |
| 101–200 | Unhealthy | Unhealthy (Sensitive) / Unhealthy | 35–150 μg/m³ |
| 201–300 | Very Unhealthy | Very Unhealthy | 150–250 μg/m³ |
| 301+ | Hazardous | Hazardous | 250+ μg/m³ |
Singapore uses PSI for official health advisories — third-party apps showing US AQI may differ slightly. Use haze.gov.sg (NEA) during haze events.
The Peatland Crisis: Why Fires Keep Coming
What is tropical peatland?
Peatland is waterlogged soil made of partially decomposed plant matter, accumulated over thousands of years. Indonesia holds ~50% of the world's tropical peat — the Riau province of Sumatra and Central Kalimantan hold the largest deposits. When drained for palm oil or pulpwood plantations, the peat dries out and becomes highly flammable.
Why do fires keep happening?
Slash-and-burn (tebang bakar) land clearing is cheap and traditional. Even when banned, enforcement in remote Kalimantan and Sumatra is weak. Major palm oil concession holders face legal accountability under Indonesian law, but prosecution is slow. El Niño drought years dry peat to a depth of several metres — a single ignition can smoulder underground for months, impossible to extinguish.
Singapore's legal response
The Transboundary Haze Pollution Act (2014) allows Singapore to sue foreign companies causing Singapore haze — a world first. The act has been used to serve legal processes on Indonesian palm oil companies. Separately, Singapore's NEA operates a satellite-based hotspot detection system monitoring fire locations in Sumatra and Kalimantan daily during haze season.
Singapore Green Plan 2030
For local sources, Singapore's Green Plan 2030 targets: all new vehicle registrations electric by 2030; 2 GWp solar panels deployed by 2030; reduce domestic energy waste 20% vs 2005. Since local sources are minimal, the plan's air quality benefits are modest — Singapore's air problem is primarily transboundary, not domestic.
Southeast Asia City AQI Comparison — 2024 Annual Averages
| City | Annual AQI | Primary Source |
|---|---|---|
| Jakarta | 125 | Indonesia capital, traffic + industry |
| Hanoi | 115 | Vietnam, coal + biomass burning |
| Kuala Lumpur | 92 | Haze + traffic, KL |
| Bangkok | 88 | Diesel vehicles, crop burning |
| Manila | 82 | Jeepneys, construction dust |
| Ho Chi Minh City | 78 | Vietnam south, motorbike fleet |
| Singapore | 58 | City-state: strict controls + haze |
| Yangon | 72 | Myanmar, biomass + diesel |
Estimates based on IQAir + WHO 2024 data. Singapore's apparent advantage is partly offset by occasional severe haze spikes.
Health Advisory: Singapore Haze Action Plan
PSI 0–100 (Normal)
Normal activities. No restrictions. Healthy adults can exercise outdoors freely. This is Singapore's typical state November–April.
PSI 101–200 (Unhealthy)
Sensitive groups (elderly, children, asthma, heart conditions) reduce prolonged outdoor exertion. Healthy adults limit strenuous outdoor exercise. Keep indoor air clean — windows closed, air purifier running.
PSI 201–300 (Very Unhealthy)
Everyone should avoid prolonged outdoor activity. N95 masks required outdoors. Construction outdoor work restricted under Singapore law. Schools may implement indoor activity guidelines. Minimise time outdoors.
PSI 301+ (Hazardous)
Schools closed. Avoid all non-essential outdoor activities. N95 masks mandatory outdoors. NEA distributes free N95 masks at community centres. Seal windows and doors. Run air purifiers continuously. Seek medical advice immediately if experiencing respiratory distress.
FAQ: Singapore Air Quality
What is Singapore's annual average AQI?
Singapore's annual average AQI is approximately 58 (Moderate) — one of Southeast Asia's best. This reflects strict local air quality controls: Euro 6 vehicle standards, LNG power generation, and no heavy industry in the city-state. The caveat is haze season (June–October) when Indonesian peatland fires can push daily PSI above 200 for days at a time, skewing the annual average upward significantly in El Niño years.
What is the difference between PSI and AQI in Singapore?
Singapore uses the Pollutant Standards Index (PSI), developed in the 1970s and updated in 2014 to include a 24-hour PM2.5 sub-index. The US EPA AQI uses a different calculation formula and different breakpoints. For PM2.5 specifically, PSI and AQI values track closely — PSI 100 ≈ AQI 100–110. However, for PM10 and SO2, PSI and AQI diverge significantly. During haze events, always use NEA's PSI (not third-party AQI apps) as the official Singapore health guideline benchmark.
Why does Indonesia's peatland burning affect Singapore so severely?
Sumatra and Kalimantan contain the world's largest tropical peatland deposits — organic carbon stored up to 20 metres deep. When land is drained for palm oil or pulpwood plantations and fires set (intentionally or via escaped smallholder fires), peat smoulders underground for weeks or months, releasing enormous smoke volumes. The 2015 El Niño haze: an estimated 2.6 billion tonnes of CO2 equivalent was released in just a few months. The Southwest monsoon (May–October) carries this smoke directly toward Singapore and Peninsular Malaysia in 12–36 hours.
What is the ASEAN Transboundary Haze Pollution Act?
Singapore passed the Transboundary Haze Pollution Act (THPA) in 2014 — the world's first law allowing a country to sue foreign companies for causing cross-border pollution. Under THPA, Singapore can prosecute companies with operations in Indonesia if they are found responsible for fires that cause haze in Singapore. As of 2024, no successful prosecutions have been completed due to jurisdictional and evidence challenges, but the law serves as a significant diplomatic and reputational pressure tool.
When is the best time to visit Singapore for air quality?
December through April offers the cleanest air. The Northeast monsoon brings clean air from the South China Sea and avoids Indonesian fire regions. AQI regularly stays below 50 (Good). The inter-monsoon months of April–May carry some haze risk. Avoid August–September in La Niña or El Niño years when Kalimantan peatland fires peak. Always check NEA's haze outlook (haze.gov.sg) before planning extended outdoor activity during June–October.