The Royal Children’s Hospital said there was no unusual rise in the number of people presenting with asthma or similar conditions.
Pollution in the city lifted slightly overnight, before it is forecast to go down to “poor” again and then worsen on Thursday.
The Latrobe Valley is expected to have “very poor” conditions, the EPA says, while fire-ravaged towns in East Gippsland and the state’s North East remain at “hazardous” levels.
Bureau of Meteorology forecaster Michael Efron said visibility fell to just 300 or 400 metres on Monday night.
Smoke from East Gippsland and the NSW south coast has blanketed parts of New Zealand in haze, and Mr Efron said there were reports of it reaching as far as Argentina and Chile.
“It just shows that the smoke, once it gets into the upper atmosphere, it does travel a significant distance around the Southern Hemisphere.”
He said smoke from East Gippsland was blowing onto the Bass Strait and then onto Melbourne from there.
Haze could worsen on Thursday when the smoke will instead likely be dragged directly across the state.
“On Thursday it won’t be travelling out onto the water, it’ll just be travelling over the land from East Gippsland and the North East, right over the central district,” Mr Efron said.
Visibility was down to two kilometres in Mildura, Swan Hill and Horsham on Tuesday morning.
“Basically the entire state is covered in smoke haze at the moment.”
Air quality in Melbourne was the equivalent of smoking four cigarettes on Monday, according to calculations by University of Melbourne Professor Peter Rayner.
“I think yesterday’s air quality in Melbourne was like every person (child and adult) smoking about four cigarettes. It’s worse the closer you get to the fires as you might expect,” Professor Rayner said.
He compared data from the EPA to analysis by Californian climate science not-for-profit Berkeley Earth to come to that conclusion.
A change on Friday will blow the smoke away from Melbourne, but cause a spike in the fire risk for the danger zones.
“Given the strength of that change we would expect a significant improvement in visibility,” Mr Efron said.
“Obviously Friday is looking like a spike day in terms of the fire danger with that change crossing the state so we do get that combination of hot air, gusty winds and quite dry air as well across the state, especially the eastern districts where we have those fires going at the moment.”
Victoria’s chief health officer Dr Brett Sutton on Monday warned that “very poor” air quality could be fatal for vulnerable people, including those with heart and lung disease or diabetes, children under 14, people over 65 and pregnant women.
They should avoid exercise and stay indoors, Dr Sutton said.
Concerned Melburnians rushed to hardware stores to pick up P2 or N95 smoke masks – the only models Dr Sutton said could properly filter smoke, with generic face masks or bandanas ineffective.
Yet supply was limited on Monday. Officeworks said it had no stock remaining in Victorian stores, while a spokeswoman at Bunnings Warehouse in Lilydale said the masks were “flying out” the store.
Bunnings stores in the city’s inner-north and inner-east, including Fairfield, Northland, Thomastown, Collingwood and Brunswick, also ran out of stock.
Sally Powell, Bunnings regional operations manager, claimed masks were available in “most” Victorian stores, but acknowledged “we are seeing increased customer demand and stock levels can change quickly”.
A Mitre10 spokeswoman said the company still had stock in its Melbourne warehouse and was prioritising sending masks to fire-affected areas.
Rachel is a breaking news reporter for The Age.