Smog

Smog is a form of air pollution that can affect human health and the environment. It appears as a brown haze in the sky and can limit visibility.

Smog happens when air emissions build up under certain weather conditions. These emissions come from many sources, including:

• industry
• motor vehicles
• home wood heaters
• burning off
• bushfires.

There are 2 different kinds of smog:

• summer smog
• autumn and winter smog.
  

Summer smog can happen in:

• Melbourne on hot days between October and March
• other parts of Victoria during bushfires.

It's caused when sunlight interacts with certain gases to form ozone. It can also contain other pollutants made up of fine particles.

Summer smog can stay over Melbourne for days when:

• weather is calm
• winds are light
• air temperatures are high.

When wind picks up, it clears the smog.

Autumn and winter smog can happen anywhere in Victoria during calm weather conditions. It results from a build-up of PM_2.5 particles in the air.

Fine particles scatter sunlight and reduce visibility. Visibility is poor when measurements in dry air between 7 am and 7 pm are below 20 km. This means you cannot see a landmark, such as a building or mountain, that is more than 20 km away.

The Environment Reference Standard sets out standards for air quality, including visibility.

Smog and the law

The general environmental duty applies to managing emissions that contribute to smog, including:

• PM_2.5 particles
• nitrogen dioxide
• volatile organic compounds.
  

Other duties and obligations may apply to managing emissions that produce smog.

Our role in smog

We monitor air quality around Victoria. We have air monitoring equipment that measures airborne gases and particles. This includes ozone and particles found in smog. The data we collect supports our daily air quality forecasts.

Learn more about how we monitor the quality of the environment.

Impact of smog on your health

Smog can be harmful to human health and the environment. When it’s smoggy outside, check air quality in your area.

PM_2.5 and other particles in smog can harm people, especially those with heart or lung conditions. If you have a heart or lung condition, follow your treatment plan or seek medical advice.

If you're concerned about your health because of air quality, find out who to contact.

Reduce smog

Emissions from vehicles, wood heaters and industry cause autumn and winter smog.

To reduce these:

• avoid driving when you can – try to use public transport, cycle or walk
• maintain your vehicle
• follow guidelines about burning off from the CFA and your local council
• use wood heaters in the right way, and do not use them when another heating source is available.

You can report smoke pollution to us. If you have concerns about wood heaters or burning off, contact your local council.