Lukas Furtenbach is a mountain guide. He helped a team from Britain climb Mount Everest very fast. They used a special gas called xenon. They left London on May 16. They climbed the mountain on May 21. They came home two days later. Some people do not like the xenon gas. It helps climbers not get sick when they are high up. Nepal is checking if it is okay. The climbers trained in special tents. They also used xenon gas in Germany. Furtenbach says it is good to spend less time on the mountain. This helps the mountain. He says the xenon gas is safe.