Numerous organizations use Hahn as a guide including Rainier Mountaineering (for which he has worked since 1986), and Fathom Expeditions. Hahn is a regular guide on Mount Rainier in Washington with more than 270 ascents, as well as a professional ski patroller at Taos Ski Valley in New Mexico where he has been employed since 1985. He has guided climbers to the summit of Cho Oyu twice, the sixth-highest mountain in the world, bordering Nepal and Tibet. Hahn has also guided former New Mexico governor Gary Johnson to the summits of Vinson and Mt. Everest.