Air Quality Singapore
PSI, PM2.5, AQI & pollutant readings
Live air quality readings are published by the National Environment Agency (NEA) on the official haze microsite. We surface the latest bands here and explain what each reading means. For real-time regional PSI and PM2.5 numbers, follow the link above.
1-Hour PM2.5 Bands
0–55
Band 1 — Normal
µg/m³ (1-hr PM2.5)
56–150
Band 2 — Elevated
µg/m³ (1-hr PM2.5)
151–250
Band 3 — High
µg/m³ (1-hr PM2.5)
≥251
Band 4 — Very High
µg/m³ (1-hr PM2.5)
24-Hour PSI Bands
| PSI Range | Air Quality Descriptor | Health Advisory |
|---|---|---|
| 0–50 | Good | Normal activities can be carried out. |
| 51–100 | Moderate | Normal activities can be carried out. |
| 101–200 | Unhealthy | Reduce prolonged or strenuous outdoor physical exertion. |
| 201–300 | Very Unhealthy | Avoid prolonged or strenuous outdoor physical exertion. |
| 301+ (Above 300) | Hazardous | Minimise outdoor activity. Wear N95 masks if you must go out. |
PSI vs. AQI — what is the difference?
Singapore PSI
The Pollutant Standards Index is Singapore’s official air quality index, used by NEA for health advisories. It is calculated from six pollutants (PM2.5, PM10, SO₂, O₃, CO, NO₂), reported as a 24-hour average, and split into 5 bands (Good → Hazardous).
Reported by region: North, South, East, West, Central.
US EPA AQI
The Air Quality Index used by the World Air Quality project (aqicn.org) and most international apps. It is calculated from PM2.5, PM10, O₃, CO, SO₂ and NO₂ over shorter averaging windows, and split into 6 bands — the key difference is a separate Unhealthy for Sensitive Groups band (101–150) that PSI does not have.
AQI values often run higher than PSI for the same air.
| AQI Range | Level | Health Implication |
|---|---|---|
| 0–50 | Good | Little or no risk. |
| 51–100 | Moderate | Acceptable; unusually sensitive people should consider limiting prolonged outdoor exertion. |
| 101–150 | Unhealthy for Sensitive Groups | Sensitive groups (asthma, heart/lung disease) may experience effects. |
| 151–200 | Unhealthy | Everyone may begin to feel effects; sensitive groups more serious. |
| 201–300 | Very Unhealthy | Health alert: the entire population is more likely to be affected. |
| 301+ | Hazardous | Health warning of emergency conditions: everyone should avoid outdoor exertion. |
Pollutant Sub-Indices
PM2.5
Fine particulate matter (≤2.5µm)
Basis: 24-hr average PM2.5 reading
Most harmful pollutant during haze; penetrates deep into lungs.
PM10
Coarse particulate matter (≤10µm)
Basis: 24-hr average PM10 reading
Larger particles from dust, smoke and vehicle emissions.
SO₂
Sulphur dioxide
Basis: 24-hr average SO₂ reading
From industrial processes and volcanic emissions.
O₃
Ozone
Basis: 8-hr average O₃ reading
Formed by reaction of sunlight with nitrogen oxides and VOCs.
CO
Carbon monoxide
Basis: 8-hr average CO reading
From incomplete combustion of fuels; reduces oxygen in blood.
NO₂
Nitrogen dioxide
Basis: 1-hr average NO₂ reading
From vehicle exhaust and power plants; only reported when ≥1130µg/m³.
Health Advisory by PSI Range
Good / Moderate (PSI 0–100)
- Normal activities can be carried out
- No special precautions needed
Unhealthy (PSI 101–200)
- Reduce prolonged or strenuous outdoor exertion
- Elderly, pregnant women and children should minimise outdoor activity
- People with heart or lung disease should avoid outdoor activity
Very Unhealthy (PSI 201–300)
- Avoid prolonged or strenuous outdoor physical exertion
- Wear N95 masks when going outdoors
- Close doors and windows; use air purifiers indoors
Hazardous (PSI > 300)
- Minimise all outdoor activity
- Wear N95 masks if outdoors is unavoidable
- Seek medical attention if you feel unwell
Related Information
Air quality in Singapore — what to know
Singapore air quality is monitored continuously by the National Environment Agency (NEA) through a network of air quality monitoring stations across the island. The two most-watched indicators are the 24-hour PSI (Pollutant Standards Index) and the 1-hour PM2.5 reading. This page explains the bands, the sub-indices behind PSI, and the health advisories tied to each range.
PSI vs. PM2.5 — what is the difference?
The PSI is a composite index calculated from six pollutants — PM2.5, PM10, sulphur dioxide (SO₂), ozone (O₃), carbon monoxide (CO) and nitrogen dioxide (NO₂). The highest sub-index becomes the overall PSI. The 1-hour PM2.5 reading, on the other hand, is a fast-updating single pollutant measurement reported in µg/m³ and split into four bands (Normal, Elevated, High, Very High). PM2.5 is the most relevant pollutant during haze episodes because fine particles penetrate deepest into the lungs.
PSI vs. AQI — which one should I use?
Use the PSI for official NEA health advisories in Singapore — it is the index that schools, agencies and local media quote. Use the AQI when comparing Singapore air quality with international readings on apps such as aqicn.org, or when you care about the Unhealthy for Sensitive Groups band that AQI has but PSI does not. The two indices also use different averaging windows, so the AQI value for the same air can differ from the PSI value — typically the AQI reads higher than the PSI during haze.
Singapore air quality today
For Singapore air quality today, check the 1-hour PM2.5 band first — it updates hourly and is the earliest signal of deteriorating air. The 24-hour PSI is a smoother indicator used for longer-term health advisories. Both are reported by region (North, South, East, West, Central) because conditions can vary across the island. Visit the haze situation page for the regional map and the official haze microsite for live numbers.
What causes poor air quality in Singapore?
Day-to-day air quality is mostly good. Poor air quality is typically caused by transboundary haze from regional land and forest fires, usually during the dry Southwest Monsoon season (June–September). Volcanic ash, industrial accidents and local vehicle emissions can also affect readings. When the PSI climbs above 100, NEA issues health advisories and schools may scale back outdoor activities.
How to protect yourself during poor air quality
- Check the PSI today and PM2.5 band before heading outdoors
- Wear an N95 mask if the PSI is in the Unhealthy range or higher
- Close windows and use an air purifier indoors
- Reduce prolonged or strenuous outdoor physical exertion
- Watch for symptoms like coughing, shortness of breath or eye irritation
NEA Weather SG republishes guidance based on publicly available data from NEA and the Meteorological Service Singapore. For live regional readings, visit haze.gov.sg. We are not affiliated with NEA.