As the mountain side turns red, smoke fills the Sydney air, blanketed by hazardous gases. Even as firefighters battled the raging fire in New South Wales (NSW), the Australian military has been asked to prepare to face what many see as a doomsday disaster.

There are 56 fires still active across NSW on Monday, 12 of which are still uncontained. However, the focus is on the large State Mine fire near Lithgow, which reports on Saturday said, started on land belonging to the Australia Defence Force.

Although the NSW Premier Barry O'Farrell refused to speculate on the causes of the State Mine fire, preferring instead to wait for facts, the Rural Fire Services reported that it began on defence land.

Sydney, meanwhile, awoke to hazardous air quality. Reports say the quality of air Sydney exceeded that prescribed by national health standards with particles from bush fire smoke having set in over the city's atmosphere. Particularly affected areas include Sydney east to south west, north west and the Illawarra.

On Sunday, the government issued the Disaster Declaration Order considering that, "widespread danger to life and property" existed. It called on families either, evacuate on their own or face forced evacuations.

"The RFS Commissioner has advised weather conditions over the next few days will deteriorate significantly and there is potential for a significant and widespread danger to life and property across the state," Mr O'Farrell said.

The RFS Commissioner Shane Fitzsimmons has been at the centre of the action.

He terms the fire as "a whole new ball game" for residents and firefighters.

Nobody knows what might happen. The fear of the fires merging is a scenario that authorities are closely watching out for, and fear.

"I don't think I've ever use the word mega-fire," Mr Fitzsimmons said.

"But the reality is that the modelling indicates that there's every likelihood that in the forecast weather conditions that these two fires, particularly up in the back end of the mountains, will merge at some point,'' he said.

Firefighters are desperately seeking providential intervention. They need assistance from the weather, in the form of a cold change or substantial downpours, report say.

But till now the NSW weather seems to be in no mood to cooperate. Rather than cooling down the weather, the state is expected to further heat up and the winds too are picking up, leaving firefighters and residents with a feeling of doomsday coming.