Four British climbers have sparked controversy by preparing for their climb of Mt Everest with xenon gas. Photo / Getty Images
A group of British men went from London to the summit of Everest and back in less than a week with the help of xenon gas. Mountaineers and the Nepalese government weren’t pleased.
Climbing Mt Everest typically takes weeks, with most of that time spent at the foot of the mountain adjusting to the thin air. But four British men last week shrank that timeline dramatically, travelling from London to the summit and back in less than a week, according to the organiser of their expedition.
They skipped the adjustment period, in part, by inhaling a secret weapon: xenon gas.
Their feat has roiled the world of mountaineering and prompted an investigation by the Nepalese Government, as use of the gas is fiercely debated. Some research has shown that xenon can quickly acclimatise people to high altitudes, even as some experts say the benefits, if any, are negligible and the side effects of its use remain unclear.
Organisers said the gas was key to the speed of the climb, but their approach has prompted a broader debate that strikes at the core of mountaineering: should scaling Mt Everest, one of sporting’s greatest accomplishments, be made easier – available to more people during a quick vacation – with the help of a performance enhancer?
“It is a provocation, especially for traditional mountaineers, who feel bad about this idea that you can climb Everest in less than a week,” Lukas Furtenbach, who organised the exhibition, said in a phone interview from the base of the mountain. “This showed that it can work.”
Furtenbach said that beginning in 2026 he planned to offer two-week round-trip excursions to Mt Everest using xenon gas, cutting the typical time needed to scale the mountain by several weeks.
“This can be the future of commercially guided mountaineering on Mount Everest,” he said.
For those who live at lower elevations and have travelled to the mountains, the discomfort of altitude sickness is all too clear. Symptoms include nausea, headaches and disrupted sleep, and in some cases it can lead to brain swelling or even death.
As you go higher, less oxygen is absorbed into the bloodstream with each breath. That is why so many people who climb Everest use supplemental oxygen.
Xenon, an odourless gas, has been known for years to activate a molecule called the hypoxia-inducible factor, which is also turned on when people acclimate to low oxygen, said Hugh Montgomery, a professor of intensive care medicine at University College London and a mountaineer who led an expedition to Mt Everest to study how humans respond to low oxygen.
“So what these people claim to have done,” he said, “is basically found a way to switch on the adaptation to low oxygen levels.”
The group took what was known from medical science, he said, “and have now applied it, recreationally, to sport mountaineering”.
Montgomery said scientists were still unsure how xenon triggers this response.
While some doctors have used the gas in the past to “precondition” patients to low oxygen levels – for example, before major heart surgery – the practice hasn’t really caught on because “it hasn’t been as protective as one would hope,” he said.
Mike Shattock, a professor of cellular cardiology at King’s College London, said “xenon probably does very little, and there is virtually no reputable scientific evidence that it makes any difference”.
Experts cautioned that self-medicating with xenon, which has the effects of anaesthesia, could lead to overdose or death, and more study was needed to understand how the gas works and its use in mountaineering.
On Mt Everest, the weeks of training and acclimation on the lower levels of the mountain are typically required to survive the “death zone,” the area above 26,000 feet (7925 metres) where the air is particularly thin.
The British group, which included four former special forces members, took a different approach.
About 10 weeks before the expedition, the men began sleeping in hypoxic tents, which lower oxygen levels in the air and gradually acclimatised the hikers to conditions on Mt Everest, Furtenbach said.
While hypoxic tents have been used by some climbers for years, the big innovation for the British expedition came two weeks before the excursion, when the men flew to Limburg, Germany, outside Frankfurt, where a doctor, Michael Fries, had been experimenting with inhaled gases in his clinic.
The men wore masks hooked up to ventilators as an anaesthetist slowly introduced higher levels of xenon into their systems.
Furtenbach, who has tried xenon gas on his own mountaineering trips since 2020, said that after the treatment, users experienced enhanced breathing and the sensation of more lung volume, and “when you do your workout or training, you feel better”.
After arriving at the base of Everest, the British group climbed to the summit in less than three days, which Furtenbach said was one of the fastest times for a group that hadn’t acclimatised on the mountain. (According to the Nepalese Government, the record for the fastest climb overall is held by Lakpa Gelu, a Sherpa, who reached the top of the mountain in just under 11 hours.)
The rapid climb by the British expedition and the use of the gas caught the eye of the Nepalese Government, and the fallout has been swift.
Himal Gautam, director of Nepal’s tourism department, which is responsible for regulating expeditions on the nation’s mountains, said in an interview that using the gas was “against climbing ethics,” and that it would hurt the country’s tourism industry and the Sherpas who help climbers by reducing their time on the mountain.
Gautam said his department was looking into the use of the gas by the British climbers, one of whom, Alistair Carns, is also a member of Parliament.
In an interview, Carns said that his expedition had been in touch with the ministry and clarified with the department that it had not taken the gas on the mountain.
He added that many people who want to climb Mt Everest don’t have the time to spend multiple weeks acclimating.
“The reality is if I had six to eight weeks to climb Everest, I would, but I’m a government minister, and I don’t have time,” he said. “What we’ve done is we’ve proven that you can reduce the timeline safely.”
Others in the mountaineering community have warned against the use of the gas.
In January, the International Climbing and Mountaineering Federation, a global network that promotes and protects the sport, released a statement that said there was no evidence that xenon gas improved performance, adding that “inappropriate use can be dangerous”.
The federation noted that xenon has been on the World Anti-Doping Agency’s list of banned substances since 2014 and is not approved in all countries.
“From a medical point of view, off-label use without a scientific basis and with unknown health risks must be rejected,” the statement said.
Furtenbach argued that his expeditions were still using Sherpas – five accompanied the British climbers to the summit – and that shorter times on the mountain were safer, as they reduce the chance that climbers will be exposed to other health threats, including avalanches, hypothermia or falls.
He said the prohibition of the gas by the World Anti-Doping Agency didn’t apply to mountaineering because it is not a regulated competitive sport.
Use of the gas gets at a core question about why people climb mountains in the first place, Montgomery said.
“Is it really a good idea that we can all have what we want, when we want, as quick as we want?” he asked. “Are we missing out on the sacrifice you sometimes have to make to get the achievement?”
“I’m not a critic,” he added. “But maybe just bagging every hill at speed means you miss out on the joy you could have had.”
This article originally appeared in The New York Times.
Written by: Jonathan Wolfe and Bhadra Sharma
©2025 THE NEW YORK TIMES
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