There are concerns over the long-term health effects on those fighting bushfires in Australia.
Firefighters have been pushed to breaking point as the fires continue to ravage the country, with Defence Force personnel from Australia and New Zealand also assisting in the battle.
The hazards of fighting fires in such challenging conditions could have serious long-term effects for those battling the blazes, says David McBride, an associate professor of occupational and environmental medicine at the University of Otago.
"They push themselves to the limit - they can suffer heat stress, which is a life-threatening injury, and end up with chronic bronchitis and asthma," McBride told Newshub.
More than 2000 houses have been destroyed in the fires so far, and at least 25 people killed since October. The fires have burned through more than 6 million hectares across the country.
"The forest is so dry it explodes into flames and traditional firefighting methods just don't seem to be working," says Dr McBride.
"Huge clouds of smoke get charged and then they cause fire tornadoes. At least one truck has been overturned by such a tornado and one person killed because of that."
Mental health impacts are also a major concern, says Dr McBride.
Conditions eased earlier this week, allowing firefighters a window to work on crucial backburning operations. But since Thursday conditions have worsened, with experts warning there is a danger that fires from New South Wales and Victoria could merge to form a 'mega-fire'.
Kiwi firefighters have also been deployed across the Tasman. On Wednesday a team of 21 arrived in Australia, bringing the number of New Zealand firefighters sent since October to 179.
On Thursday, personnel from the New Zealand Defence Force were sent to offer assistance.
They will go wherever they are needed to move people and deliver crucial supplies.
On Thursday, bushfires intensified on Kangaroo Island, in South Australia, while the state of Victoria extended a state of disaster, which now covers almost half the entire eastern half of the state.