Live PSI / PSI guide & FAQ
Haze 101
Singapore PSI explained & FAQ
PSI is the number Singapore checks before deciding between a run, a mask, or a very long lunch indoors. Here is what it measures, what the bands mean, and when to expect haze.
What is the PSI?
The Pollutant Standards Index (PSI) is the National Environment Agency’s (NEA) air-quality scale for Singapore. The 24-hour PSI is based on six pollutants: fine particulate matter (PM2.5), PM10, sulphur dioxide, nitrogen dioxide, carbon monoxide and ozone. NEA publishes readings for the Central, North, South, East and West regions, and the highest regional reading is what NEA headlines.
PM2.5, the tiny particles that travel deep into the lungs, is reported separately as a concentration in µg/m³ and is usually the pollutant that drives PSI up during haze.
Official NEA PSI bands
| Descriptor | 24-hour PSI | General guidance |
|---|---|---|
| Good | 0–50 | Normal activities. |
| Moderate | 51–100 | Normal activities. |
| Unhealthy | 101–200 | Reduce prolonged or strenuous outdoor physical exertion. |
| Very Unhealthy | 201–300 | Avoid prolonged or strenuous outdoor exertion. |
| Hazardous | 301 and above | Minimize outdoor activity. |
Always follow the latest advisories on haze.gov.sg. If you have heart or lung conditions, are pregnant, elderly, or caring for young children, speak to your doctor about precautions.
The HazePun scale (for fun)
HazePun pairs the official PSI bands with puns and mascot reactions for a lighter take on daily air-quality updates.
| HazePun tier | PSI | The vibe | Plain advice |
|---|---|---|---|
| Clean | 0–50 | Fresh & crisp! Inhale the tropical goodness. | Normal outdoor activities for everyone. |
| Moderate | 51–100 | Slight haze in the air. Still un-hazed! | Normal activities. |
| Unhealthy | 101–200 | Smells like someone is burning leaves in Sumatra. | Reduce prolonged or strenuous outdoor physical exertion. |
| Very Unhealthy | 201–300 | The air is thick. Keep your N95 glued on. | Avoid prolonged or strenuous outdoor exertion. |
| Hazardous | 301+ | Apocalyptic vibes. Set hazers to maximum survival! | Minimize outdoor activity. |
What the Merlion is wearing
| Reading | Merlion gear | Mood |
|---|---|---|
| PSI 0–50 | No mask, big wave | The Merlion is thriving and waves hello. |
| PSI 51–75 | Reaching for a cloth mask | Early warning: the mask is out, but not on yet. |
| PSI 76–100 | Cloth mask on | Mask on, ear loop adjusted, still composed. |
| PSI 101–200 | Fitted N95 respirator | Worried crouch. The puns get worse. |
| PSI 201–300 | Twin-filter respirator | Tense, with slightly red eyes. |
| PSI 301+ | Full-face gas mask | Frightened, watery red eyes behind the lenses. |
When is haze season in Singapore?
Haze is mostly transboundary: smoke from peatland and forest fires in parts of Sumatra and Kalimantan drifts to Singapore when winds blow from the south or southwest, typically during the drier southwest monsoon from about June to October. Severity swings widely year to year. Notable episodes include 1997, 2013, 2015 and 2019, and some years pass with barely a smudge.
Frequently asked questions
What is the PSI in Singapore right now?
HazePun shows the live 24-hour PSI for Singapore’s Central, North, South, East and West regions, highlighting the highest regional reading and average PM2.5. It refreshes every 15 minutes from the official National Environment Agency feed, so open hazepuns.live for the latest reading.
What does PSI mean?
PSI stands for Pollutant Standards Index, the scale Singapore’s National Environment Agency (NEA) uses to report air quality. The 24-hour PSI is calculated from six pollutants: PM2.5, PM10, sulphur dioxide, nitrogen dioxide, carbon monoxide and ozone. Official bands are Good (0–50), Moderate (51–100), Unhealthy (101–200), Very Unhealthy (201–300) and Hazardous (301 and above).
Is it safe to go outside in Singapore today?
Check the 24-hour PSI and follow NEA and Ministry of Health advisories. As a rule of thumb, normal activities are fine while the PSI is in the Good and Moderate bands (0–100), and prolonged or strenuous outdoor exertion should be reduced once it reaches Unhealthy (101 and above). HazePun is for information and entertainment, not medical advice.
Where does HazePun get its haze data?
All readings come from the National Environment Agency via the Data.gov.sg real-time PSI API. HazePun is an independent project and is not affiliated with NEA or the Singapore Government.
How do HazePun’s tiers correspond to the official PSI bands?
HazePun’s tiers follow Singapore’s official 24-hour PSI bands (Clean 0–50, Moderate 51–100, Unhealthy 101–200, Very Unhealthy 201–300, and Hazardous above 300) so the Merlion’s reactions and advisories directly reflect official health guidance.
When is the haze season in Singapore?
Transboundary haze typically appears during the drier southwest monsoon months, roughly June to October, when peatland and forest fires in parts of Sumatra and Kalimantan are carried towards Singapore by the prevailing winds. Conditions vary a lot from year to year, and some years bring little or no haze.
Why does the Merlion wear a mask?
The Merlion mascot reacts to the live PSI. It waves bare-faced when the air is clean, reaches for a cloth mask as the reading rises, then upgrades to an N95, a twin-filter respirator and finally a full-face gas mask when the air turns hazardous.
How do I share a haze pun?
Tap “Share this” on the homepage to pass the pun along on WhatsApp, Telegram, X or Facebook, or to download a ready-made share card. Every share link previews with the Merlion, the current air-quality mood and the pun.