Grant Aitken was just 12 years old when the Rural Fire Service came knocking at his Blue Mountains school west of Sydney, delivering a talk that would change his life.

Though he wasn't allowed to start active duties until he was 16, Aitken decided then and there to join Australia's volunteer firefighting corps, one of some 70,000 unpaid men and women on the frontline of the nation's regular fire emergencies.

He saw his first action as a teenager just one year after commencing duties in 1997, when he took time out between exams to battle an inferno at Oberon to the west of the mountains.

"Really I just wanted to help," he said adding that he joined the local fire brigade after seeing the dramatic consequences of blazes.

"I remember in 1994, when I was a bit younger, the Grose (Valley) going up, and as a kid watching the public panic.

"So in '97, when I was old enough to join, I was straight in there to sign up."

Three times the size of Australia's serving military, the Rural Fire Service -- the New South Wales state organisation with sister groups in Australia's seven other states and territories -- is the backbone of firefighting operations during Australia's dangerous summer months.

Australian Prime Minister Tony Abbott has been a volunteer firefighter with the RFS for a decade and helped locals with firefighting operations last weekend.

Employers are required by law to release members from their day jobs when there are fires burning and most people -- particularly those in bush areas -- know someone who serves in the RFS.

Now 31, and with some 16 years' experience, Aitken is a deputy captain, with the mixed blessing of being between jobs meaning he is one of the first on call.

He has been on rotating shifts for a week after a sudden firestorm swept through parts of the mountains, razing more than 200 homes. He was on the ground that day battling to save homes.

"Thursday and Friday (last week) down at Winmalee, that was actually pretty horrific, the fire ran hot it ran hard and we were pretty much trying to get everywhere, it was a bit hectic," he told AFP.

"It's hard to describe, because you've got the heat off the fire plus the heat off the weather. It's extremely hot and it's exhausting work. I can't really describe it, it's one of those situations where you've got to be there to experience it."

On days like those Aitken runs on adrenaline and it isn't until some four or five days later that he says the stress and trauma hit home.

There are RFS chaplains the crews can talk to but Aitken says his way of coping is to talk things through his family, particularly his wife who is also a firefighter.

Friendship with his fellow crew members is also vital, both on and off the ground.

"It's very important because if you don't have that camaraderie out there on the fire front and you can't trust the person next to you, that's when bad things happen," he said.

Aitken is manning the communications caravan at Mount Victoria, relaying messages between crews on the ground and operational headquarters -- a psychologically testing task on high-risk days like Wednesday, with gale-force winds and intense heat hampering crews battling several major blazes in the Blue Mountains.

As is the case with many RFS crews, Aitken has left his own property at Woodford, in the path of Wednesday's fires, to complete his volunteer duties.

He is pragmatic about the dangers.

"For people who live in these communities fire's always going to be a part of their lives because we live in a bushfire prone area," he said.

Aitken's parents live with him and his wife, and they have spent the last seven days preparing for Wednesday's severe risk.

All too often in wildfire emergencies RFS volunteers who have abandoned their homes to protect others do lose everything, and Aitken said it is "hard to describe that feeling, what you feel for the guys. It's one of those things you just don't want to think about".