He has seen teammates killed by avalanches and rescued climbers on Everest, but Andrew Lock keeps going back for more.
Mr Lock, who has been awarded the Medal of the Order of Australia (OAM) for his services to mountaineering, is the first Australian to climb all of the world's 14 peaks over 8000 metres, and to lead a commercial expedition to the summit of Mount Everest.
This month he returned home to accept the Queen's Birthday accolade after attempting to climb Everest again - this time without oxygen.
It was not always the most pleasant experience, Mr Lock told AAP. "You have this almost constant wind battering the mountain ... and compounding that the available oxygen is about one-third of what we have at sea level, which means that you are just dying, literally dying," he said.
"The high winds were not forecast ... so I had to make the decision to risk frostbite or fight another day.
"I chose my nose." Although the 49-year-old "doesn't scare easy", he admitted that some moments have had him spooked.
In 2005, Mr Lock climbed Annapurna in Nepal - notorious for being the world's deadliest mountain.
"Every route on the mountain is threatened by massive avalanches ... about 130 people have climbed it, and over 60 climbers have died in the attempt."
That year an avalanche hit Mr Lock and his team, killing one climber. But he went back in 2007 and tried again.
"It was a very nervous expedition ... I'll never set foot on Annapurna again."
Despite the risk of death and frostbite, the Canberra resident can't stop climbing.
"When you can continue in the face of fear that's a very empowering feeling and to overcome that in a period of sustained intensity ... there's quite some euphoria that comes with overcoming all those challenges and beating yourself."