The death zone on Mount Everest is an area above a certain altitude where the pressure of oxygen is insufficient to sustain human life for an extended time span. This point is generally tagged as 8,000 meters (26,000 feet) above sea level, where atmospheric pressure is less than 356 millibars (10.5 inHg; 5.16 psi) . In the death zone, climbers brains and lungs are starved for oxygen, their risk of heart attack and stroke is increased, and their judgment quickly becomes impaired. An extended stay above 8,000 meters without supplementary oxygen will result in deterioration of bodily functions and death. Climbers may also experience heart attack, stroke, or severe altitude sickness. Other dangers posed by the death zone are snow blindness and frostbite. The temperatures on Mount Everest are low enough to freeze skin instantly. Many deaths in high-altitude mountaineering have been caused by the effects of the death zone, either directly by loss of vital functions or indirectly by wrong decisions made under stress, or physical weakening leading to accidents.