FOR those close to the fires, the conditions could be best described as being similar to the fire-bombing that destroyed German cities such as Dresden in World War II.

A University of Melbourne senior lecturer in fire ecology and management, Kevin Tolhurst, said the radiant heat - the heat given off by the fires - would itself have been enough to kill. "When it gets close, you have enormous radiation loads."

The "survivability" distance of Saturday's heat was about four times their height - a 35-metre high fire would directly imperil those within 140 metres.

The body would get over-stressed, the core temperature would get too high and the metabolism would break down in those conditions. He said bushfires produce their own volatile gases which in turn burn - and on a day as hot as Saturday, it does not take much for them to ignite.

Dr Tolhurst said people could be surrounded by a series of spot fires. Breathing would become difficult due to burning gases and the body would dehydrate quickly. Death from a form of asphyxiation was also possible.

He said the fires were slightly different from those on Ash Wednesday, when they moved more quickly. Hotter temperatures on Saturday meant the fire was even more intense and areas caught alight more easily. Combined with the speed of the fires generated by the volatile winds, it would have left many people with little time to respond.

A Monash University associate professor, Jason Beringer, said the meteorological conditions on Saturday were second in severity only to Black Friday, the fires that devastated Victoria in 1939.

But he thinks the fires could have been even worse. He said it was likely most of Saturday's fires were either deliberately lit or accidentally started by people, rather than by lightning.

Professor Beringer said the State Government had done a good job preparing for bushfires but the conditions on Saturday were too extreme.