What is PM2.5 and why does it matter?

PM2.5 is airborne particles smaller than 2.5 micrometres, measured in micrograms per cubic metre (µg/m³). They are small enough to be breathed deep into the lungs, and wildfire smoke is rich in them.

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How it is reported

NEA publishes an hourly PM2.5 reading for five regions in four bands: Normal (0–55), Elevated (56–150), High (151–250) and Very High (251 and above).

Why smoke is mostly PM2.5

Combustion, especially smouldering peat, makes very fine particles that stay in the air for a long time and travel far.

Related guides

Understand the causes

Why peat fires make such dense haze

Sources

NEA 1-hour PM2.5 readings (Singapore) — National Environment Agency (NEA), Singapore · official site · API / docs
NEA 24-hour PSI (Singapore) — National Environment Agency (NEA), Singapore · official site · API / docs

General information, not medical advice. Follow your doctor and your school, league or organiser's final call. Data come from official sources; see data sources.