Fig 1 Deaths on standard north and south routes of Everest during spring climbing season (April-June) 1982-2006. Deaths during descent are above route profile and deaths before summiting or during bids for summit with unknown outcome are below. One sherpa died below Yak camp during evacuation. Right axis shows estimated barometric pressure during May,14 and percentage of oxygen at sea level (760 mm Hg) that exerts equivalent partial pressure to atmospheric oxygen at relevant altitude. Left axis shows estimated ambient air temperature during May.15 16 Scale on x axis is expanded by factor of two for route above 8000 m. *Two sided Fisher’s exact test