Canberra's air quality was again the worst of any major city in the world on Thursday, due to smoke from bushfires on the NSW south coast.
Conditions had even affected some MRI machines at Canberra Hospital, leading to the cancellation of some procedures.
However, a spokesman said the hospital was still meeting demand.
Australia Post has also suspended mail deliveries in Canberra until further notice. On Thursday, it apologised for inconvenience to customers, but said staff safety was a priority.
A global air quality index ranked Canberra's air worse than New Delhi, India or Lahore, Pakistan, on Thursday.
Air quality in Canberra was more than 10 times hazardous levels, on Thursday, according to local health authorities. It peaked at more than 20 times hazardous levels on Wednesday.
The smoke is expected to linger over the national capital in coming days. The Bureau of Meteorology says high temperatures are trapping the smog.
Conditions have been even worse in the NSW coastal town of Bateman's Bay, which has been besieged by fires in recent days. Its air quality was rated nearly twice as bad as Canberra earlier on Wednesday.
There are out of control fires burning near Kosciuszko National Park to Canberra's west, and the fires along the coast to the east.
Canberra’s #AirQuality is currently rated as worse than any other major city in the world, reaching levels more than 20 times that considered as hazardous.
Across Australia, as the smoke haze continues to affect us, here’s what you can do. #AusFires #BushfiresAustralia pic.twitter.com/F6OjjVxpEv
— Australian Academy of Science (@Science_Academy) January 2, 2020
Bureau forecaster Abrar Shabren said the widespread fires meant that whatever the wind change, smoke would still be blown across the territory.
"It will persist over the next couple of days. We will see a change, probably tomorrow," he said.
Hazardous levels are normally considered 200 or above, with air quality stations around Canberra recording levels between 2300 to 2800.
ACT Health has urged Canberrans to stay indoors and avoid physical activity outdoors.