Lukas Furtenbach is a mountain guide. He helped a British team 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 back home two days later. Some people do not like the xenon gas. It helps climbers not get sick on the mountain. Nepal is checking it. The climbers trained in special tents. They also used xenon gas in Germany. Furtenbach says that climbing faster is good for the mountain. But they did not use the xenon gas in Nepal. Furtenbach says it is safe for climbers.