Editing Cabin pressurization (section)

==Unplanned decompression==
{{Main|Uncontrolled decompression}}
[[File:Passenger oxygen mask dsc06035.jpg|thumb|upright|Typical passenger oxygen mask deployment]]

Unplanned loss of cabin pressure at altitude/in space is rare but has resulted in a [[Uncontrolled decompression#Notable decompression accidents and incidents|number of fatal accidents]]. Failures range from sudden, catastrophic loss of airframe integrity (explosive decompression) to slow leaks or equipment malfunctions that allow cabin pressure to drop.

Any failure of cabin pressurization above {{cvt|10000|ft|0}} requires an emergency descent to {{cvt|10000|ft|0}} or the closest to that while maintaining the ''minimum sector  altitude'' (MSA), and the deployment of an [[oxygen mask]] for each seat. The oxygen systems have sufficient oxygen for all on board and give the pilots adequate time to descend to below {{cvt|10000|ft|0}}. Without emergency oxygen, [[Hypoxia (medical)|hypoxia]] may lead to loss of consciousness and a subsequent loss of control of the aircraft. Modern airliners include a pressurized pure oxygen tank in the cockpit, giving the pilots more time to bring the aircraft to a safe altitude. The [[time of useful consciousness]] varies according to altitude. As the pressure falls the cabin air temperature may also plummet to the ambient outside temperature with a danger of [[hypothermia]] or [[frostbite]].

For airliners that need to fly over terrain that does not allow reaching the safe altitude within a maximum of 30 minutes, pressurized oxygen bottles are mandatory since the [[chemical oxygen generators]] fitted to most planes cannot supply sufficient oxygen.

In [[jet fighter]] aircraft, the small size of the [[cockpit]] means that any decompression will be very rapid and would not allow the pilot time to put on an oxygen mask. Therefore, fighter jet pilots and aircrew are required to wear oxygen masks at all times.<ref>{{cite web |url=http://goflightmedicine.com/hypoxia/ |title=Hypoxia |last1=Jedick MD/MBA |first1=Rocky |date=28 April 2013 |website=goflightmedicine.com |publisher=Go Flight Medicine |access-date=17 March 2014}}</ref>

On June 30, 1971, the crew of [[Soyuz 11]], Soviet cosmonauts [[Georgy Dobrovolsky]], [[Vladislav Volkov]], and [[Viktor Patsayev]] were killed after the cabin vent valve accidentally opened before atmospheric re-entry.<ref name="time">{{cite magazine|url=http://www.time.com/time/magazine/article/0,9171,903011,00.html|archive-url=https://web.archive.org/web/20080318094147/http://www.time.com/time/magazine/article/0,9171,903011,00.html|url-status=dead|archive-date=March 18, 2008|title=Triumph and Tragedy of Soyuz 11|access-date=20 October 2007|magazine=[[Time (magazine)|Time]] | date=12 July 1971}}</ref><ref name="ea">{{Cite encyclopedia|url=http://www.astronautix.com/flights/soyuz11.htm|title=Soyuz 11|access-date=20 October 2007|encyclopedia=Encyclopedia Astronautica|year=2007|url-status=dead|archive-url=https://web.archive.org/web/20071030215242/http://www.astronautix.com/flights/soyuz11.htm|archive-date=30 October 2007}}</ref>