KATHMANDU, Nepal: Using xenon gas treatment and new technology is making climbing Mount Everest faster and better for the environment by reducing garbage and waste, a famous mountain guide said this week.

Lukas Furtenbach led a group of British climbers who left London on May 16 and reached the 8,849-meter (29,032-foot) summit on May 21. They returned home two days later, one of the fastest Everest climbs on record, including travel time.

However, the use of xenon gas treatment has caused controversy. Nepal's mountaineering officials have said they will investigate it.

Furtenbach told The Associated Press in Kathmandu, "The only reason we use xenon is to make climbing safer and protect climbers from high altitude sickness. People die on Everest every year, and this might help make climbing safer."

The climbers trained for months, using hypoxia tents to simulate low oxygen. Two weeks before the trip, they had xenon gas treatment at a clinic in Germany.

Usually, climbers spend weeks at base camp getting used to the high altitude. They then practice climbing to lower camps on Everest to prepare their bodies for the thin air.

This new method means climbers spend less time away from home, fewer days off work, and save money.

Furtenbach said climbing faster also means less harm to the mountain's environment.

"Human waste is a big problem at Everest base camp. Spending one week there instead of eight means 75% less waste," he said. "That means much less garbage and fewer supplies to carry up the mountain."

Nepal does not have rules on how long climbers must spend acclimatizing. Climbing permits cost $11,000 each and last 90 days. The climbing season usually ends in May before the monsoon rains. Then, ropes and ladders are removed from the mountain.

Nepal's mountaineering department said it will investigate xenon gas use. Furtenbach said the gas was never used in Nepal and that he could prove it is safe for climbers.