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Room air at altitude can be enriched with oxygen without introducing an unacceptable fire hazard. At an altitude of 8000 m the equivalent altitude in terms of oxygen partial pressure can be reduced to below 4000 m without increasing the fire hazard beyond that of normal sea level atmospheric air.
In mountaineering, the death zone refers to altitudes above which the pressure of oxygen is insufficient to sustain human life for an extended time span. This point is generally agreed as 8,000 m (26,000 ft), where atmospheric pressure is less than 356 millibars (10.5 inHg; 5.16 psi). [ 1 ]
The oxygen atom product combines with atmospheric molecular oxygen to reform O 3, releasing heat. The rapid photolysis and reformation of ozone heat the stratosphere, resulting in a temperature inversion. This increase of temperature with altitude is characteristic of the stratosphere; its resistance to vertical mixing means that it is stratified.
An oxygen partial pressure equivalent to sea level can be maintained at an altitude of 10,000 metres (34,000 ft) with 100% oxygen. Above 12,000 metres (40,000 ft), positive pressure breathing with 100% oxygen is essential, as without positive pressure even very short exposures to altitudes above 13,000 metres (43,000 ft) lead to loss of ...
At 11,900 m (39,000 ft), breathing pure oxygen through an unsealed face mask, one is breathing the same partial pressure of oxygen as one would experience with regular air at around 3,600 m (11,800 ft) above sea level [citation needed]. At higher altitudes, oxygen must be delivered through a sealed mask with increased pressure, to maintain a ...
Air pressure actually decreases exponentially with altitude, for altitudes up to around 70 km (43 mi; 230,000 ft), dropping by half every 5.6 km (18,000 ft), or by a factor of 1/e ≈ 0.368 every 7.64 km (25,100 ft), which is called the scale height. However, the atmosphere is more accurately modeled with a customized equation for each layer ...
Oxygen consumption is reduced to a maximum of 1 liter per minute. [8] Travelers acclimatized to high altitudes exhibit high levels of HVR, as it provides advantages such as increased oxygen intake, enhanced physical and mental performance, and lower susceptibility to illnesses associated with high altitude. [1]
The lighter constituents atomic oxygen (O), helium (He), and hydrogen (H) successively dominate above an altitude of about 200 kilometres (124 mi) and vary with geographic location, time, and solar activity. The ratio N 2 /O which is a measure of the electron density at the ionospheric F region is highly affected by these variations. [2]