PM2.5 are very small particles usually found in smoke. They have a diameter of 2.5 micrometres (0.0025 mm) or smaller.

PM2.5 particles are a common air pollutant. We measure PM2.5 at sites around Victoria. 

Health effects of PM2.5 particles

Breathing in PM2.5 particles can affect your health. PM2.5 particles are small enough for you to breath them deeply into your lungs. Sometimes particles can enter your bloodstream.

People who are sensitive to air pollution might experience symptoms when PM2.5 levels are high. This includes people with heart or lung conditions. Symptoms can include:

  • wheezing
  • coughing
  • chest tightness
  • difficulty breathing.

If you’re worried about your symptoms, see your doctor or call Nurse on Call on 1300 606 024.

Call 000 if you experience chest pain or difficulty breathing.

Find out more about what to do when it’s smoky outside.

Sources of PM2.5 particles

Common sources of PM2.5 particles include:

PM2.5 on EPA AirWatch

We display PM2.5 data on EPA AirWatch using air quality categories. We show the average levels of PM2.5 over:

  • the last hour (1-hour average)
  • the last 24 hours (rolling 24-hour average).
Air quality category PM2.5 µg/m3 averaged over 1 hour PM2.5 µg/m3 averaged over 24 hours
Good   Less than 25 Less than 12.5
Fair   25–50 12.5–25
Poor   50–100 25–50
Very poor   100–300 50–150
Extremely poor   More than 300 More than 150

Air quality standards for PM2.5

We compare PM2.5 data to national air quality standards. These are incorporated into the State Environment Protection Policy (Ambient Air Quality).

There is currently no national standard for the one-hour PM2.5 average. For one-hour PM2.5 data, we use the value 62 µg/m3 to trigger a ‘poor’ air quality category.


National standard Averaging time
25 µg/m3 24 hours
8 µg/m3 Annual

Read more about air quality

Air pollution

Carbon monoxide in the air

Nitrogen dioxide in the air

Ozone in the air

PM10 particles in the air



Sulfur dioxide in the air

Air pollution and visibility

Vehicle emissions and air quality

Wood smoke and air quality

Clean air and future air quality

Reviewed 13 January 2021