When mountain climbers reach extreme altitudes, they run the risk of oxygen deprivation. Using oxygen tanks at high altitudes helps reduce the risk of serious injury or death.IdentificationAccording to the International Society for Mountain Medicine (ISMM), high altitude is defined as starting at 5,000 feet above sea level. The higher you climb, the less oxygen is present in the air.EffectsOne major threat of lack of oxygen is altitude sickness. Common symptoms include vomiting and dizziness. In severe cases, people with altitude sickness can develop an accumulation of fluid in the brain and lungs.BenefitsBy using oxygen tanks, high elevation climbers cut down the risk of having altitude sickness.WarningThe use of oxygen tanks does not assure there will be no risks when climbing at high altitudes. While it is vital for those climbing at extremely high levels, it is not a fail-safe against sickness.