Bushfire smoke blanketing Canberra_1

Canberra's air quality is the worst out of any major city in the world due to smoke from bushfires along the NSW South Coast.

Conditions have even affected some MRI machines at Canberra Hospital, but a health spokesman said the hospital was still meeting demand.

Australia Post has also suspended mail deliveries in Canberra until further notice, saying staff safety was a priority.

A global air quality index ranked Canberra's air worse than New Delhi, India or Lahore, Pakistan.

But conditions had been worse in the NSW coastal town of Bateman's Bay, which has been besieged by fires in recent days, rating nearly twice as bad as Canberra earlier on Wednesday.

Air quality in Canberra is more than 10 times hazardous levels according to local health authorities, having peaked at more than 20 times hazardous levels on Wednesday.

The smoke is expected to linger over the capital in the coming days, with the Bureau of Meteorology saying high temperatures were trapping the smog there.

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 this meant 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.