Since 1995, Hypoxico has designed and manufactured the patented systems that let athletes, researchers and military users simulate high-altitude conditions without leaving sea level. The New York company developed the enclosed-environment altitude-training concept and still builds its own equipment, from individual systems to facilities serving as many as 100 users. Its team draws on experience from former college athletes, elite mountaineers and performance scientists, with installations used by organizations including the United States Olympic Committee, Harvard Medical School and the Navy SEALs.