When bushfire smoke moves in, air quality can deteriorate quickly — as parts of Victoria have experienced in recent days.
Over the weekend, as several bushfires continued to burn, shifting winds pushed smoke over Melbourne, Geelong, the Bellarine Peninsula, Ballarat and the Otways, prompting authorities to issue poor air quality warnings.
Melbourne recorded the sixth-worst air quality in the world around midday on Sunday, according to IQAir. The smoke cleared the city by mid-afternoon, but the Bureau of Meteorology warned it could linger in some communities.
Six major fires continue to burn in Victoria as the state heads faces scorching conditions on Tuesday, with fire danger ratings ranging from high to extreme and temperatures forecast to exceed 40C.
With heatwave warnings also in place across the mainland, experts say Australians should stay alert for air quality warnings — in Victoria and nationally — if fires intensify or new blazes break out.
What causes smoke to spread?
Maximilien Desservettaz, a bushfire researcher at the University of Wollongong, explained that several factors affect how much smoke a fire creates and how far it can spread.
"Strong winds can disperse smoke, whereas a more stable wind is likely to keep the smoke closer to the ground where it's likely to intensify," he told SBS News.
He said that grassfires would typically create intense, fast-burning fires that don't generate as much smoke.
Whereas a fire affecting a eucalyptus or pine forest, for example, would create much more.
"That's also why hazard reduction burns can create bigger smoke impacts in communities because they're designed to be less intense than a wildfire to be kept under control," he said.
How is air quality monitored?
State and territory environment protection authorities (EPA) monitor air quality and issue warnings, as appropriate, to affected areas.
EPA Victoria has been monitoring fires across the state for a number of weeks through a network of air monitors and particle sensors.
"In addition to this, we have portable air monitoring equipment that can be deployed during a major air pollution incident," a spokesperson told SBS News.
"EPA will put out alerts during fires, floods, asthma events, major incidents like chemical spills or when hazardous material has entered the air or water."
The Bureau of Meteorology may also flag significant smoke haze in forecasts — a prompt to check local alerts — while services such as Air Quality Australia and the AirRater app provide Australia-wide air-quality readings.
When should people be checking for air quality warnings?
The EPA Victoria spokesperson said there are five levels of air quality, ranging from good, fair, poor, very poor and extremely poor.
Parts of Melbourne recorded "very poor" and "extremely poor" air quality on Sunday morning due to drifting smoke from a bushfire in the state's south-west.
"The best smoke detector is your nose and if you can smell smoke, there is always a health risk, especially for sensitive Victorians, including those with existing respiratory or other health issues," the spokesperson said.
"If you are experiencing health issues from the fires or smoke, call 000 for an ambulance if you or anyone in your care has trouble breathing, chest pain or discomfort or tightness in the chest."
The EPA recommends staying inside where possible to reduce your risk of smoke inhalation.
Desservettaz said that older homes can be "leaky" and allow undetectable levels of smoke into your home, meaning people should be proactive if smoke is affecting their area.
You can prepare your home before a smoke event by identifying any gaps and sealing these where possible. If sealing gaps is not possible, wet towels can be used to cover gaps when there is smoke outside.
Health risks
Asthma Australia said that people over 65 or 14 and under, those with pre-existing heart or lung conditions, including asthma and pregnant people are most susceptible to bushfire smoke.
They recommend people keep taking preventive medication, even if they feel well, to reduce the risk of airway inflammation and flare-ups.
Asthma Australia CEO Kate Miranda said: "Fine particles inflame the airways and make it difficult to breathe."
"Bushfire smoke can have serious health impacts for anyone with asthma, even at low levels.
"Avoid going outdoors when air quality is poor, particularly for exercise, as physical activity increases how much smoke you breathe into your lungs."
If you need to go outside when air quality is poor, EPA Victoria says a P2/N95 face mask can help — but people with pre-existing heart or lung conditions should seek medical advice first.
It recommends, when indoors, to close windows and doors until air quality improves. Using a portable air filter with a HEPA filter can also help.
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