Cabin pressurization is the active pumping of air into the cabin of an aircraft to increase the air pressure within the cabin. It is required when an aircraft reaches high altitudes, because the natural atmospheric pressure is too low to allow people to absorb sufficient oxygen, leading to altitude sickness and ultimately hypoxia. AIR is a three-letter abbreviation with multiple meanings, as described below: The Annals of Improbable Research, a monthly magazine devoted to scientific humour All India Radio - Indias Government Radio service AIR, a popular electronica band from France. ... Airbus A380 An aircraft is any machine capable of atmospheric flight. ... Airbus A380 An aircraft is any machine capable of atmospheric flight. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ... Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by lack of adaptation to high altitudes. ... Hypoxia is a pathological condition in which the body as a whole (generalized hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ...

Unpressurized flight

A lack of sufficient oxygen will bring on hypoxia by reducing the alveolar oxygen tension. In some individuals, particularly those with heart or lung disease, symptoms may begin as low as 1500 metres (5000 feet) above MSL, although most passengers can tolerate altitudes of 2500m (around 8,000 feet) without ill effect. At this altitude, there is about 25% less oxygen than there is at sea level.^[1] Alveolars are consonants articulated with the tip of the tongue against the alveolar ridge, the internal side of the upper gums (known as the alveoles of the upper teeth). ... metre or meter, see meter (disambiguation) A metre or meter[1] (symbol: m) is a unit of length and the current base unit of length in the International System of Units (SI). ... This article is about a foot as a unit of length. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...

Passengers may also develop fatigue or headache as the plane flies higher. As the operational altitude increases, reactions become sluggish and unconsciousness will eventually result. Sustained flight operations above 10,000 feet generally require supplemental oxygen (through a canula or oxygen mask) or pressurisation. A headache is a condition of mild to severe pain in the head; sometimes upper back or neck pain may also be interpreted as a headache. ... Breathing pure oxygen with a tightly sealed oxygen mask An oxygen mask provides a method to transfer breathing oxygen gas from a storage tank to the lungs. ...

Pressurized flight

Aircraft that routinely fly above 10,000 feet are generally equipped with an oxygen system fed through masks or canulas (typically for smaller aircraft), or are pressurized by an Environmental Control System (ECS) using air provided by compressors or bleed air. These systems maintain air pressure equivalent to 8000 ft or less, even during flight at altitudes above 43,000 ft. The Environmental Control System of an airplane provides air supply, thermal control and pressurization for the passengers and crew. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ... Bleed air in jet turbines is compressed air taken from within the engine, after the compressor stage(s) and before the fuel is injected in the burners. ...

As the airplane pressurizes and decompresses, some passengers will experience discomfort as trapped gasses within their bodies expand or contract in response to the changing cabin pressure. The most common problems occur with gas trapped in the gastrointestinal tract, the middle ear and the paranasal sinuses. Note that in a pressurized aircraft, these effects are not due directly to climb and descent, but to changes in the pressure maintained inside the aircraft. The gastrointestinal tract or digestive tract, also referred to as the GI tract or the alimentary canal, (nourishment canal) or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... For an alternative meaning, see ear (botany). ...

It is always an emergency if a pressurized aircraft suffers a pressurisation failure above 10,000 feet. If this occurs the pilot must immediately place the plane in an emergency descent and activate emergency oxygen for everyone aboard. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ...

History and usage of cabin pressurization

While the piston fighters of World War II often flew at very high altitudes, they were not pressurised; instead pilots used oxygen. However, in a larger bomber where crew moved about the cabin, this was considerably less practical. Therefore, the first aircraft with cabin pressurization (though restricted to crew areas), was the B-29 Superfortress. Post-war piston airliners such as the Lockheed Constellation brought the technology to civilian service, and as jet airliners were always designed for high-altitude operation every jetliner features the technology. Combatants Allies: Soviet Union United Kingdom United States and others Axis Powers: Germany Italy Japan and others Commanders Winston Churchill Franklin Roosevelt Joseph Stalin Adolf Hitler Benito Mussolini Hideki Tojo Casualties Military dead: 17,000,000 Civilian dead: 33,000,000 Total dead: 50,000,000 Military dead: 8,000... The Boeing B-29 Superfortress was a four-engine heavy bomber propeller aircraft flown by the United States Army Air Forces in World War II and other military organizations afterwards. ... President Dwight Eisenhower flew in two Constellations, named Columbine II and Columbine III. The Lockheed Constellation, affectionately known as the “Connie”, was a four-engine propeller-driven airliner built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. ...

Most turboprop aircraft also feature cabin pressurization due to their medium to high altitude operation. A very few piston-engined small private planes also do so; most do not routinely fly high enough to justify such a system. A schematic diagram showing the operation of a turboprop engine. ...

Rapid loss of pressurization (rapid decompression)

One consequence of cabin pressurization is that the pressure inside the airplane may be 10 psi (700 millibars or hPa), while the pressure outside is barely above 2 psi (15 kilopascals, 140 millibars). A harmless pinhole under these pressure differences will generate a high-pitched squeal as the air leaks out at supersonic speeds^{[citation needed]}. A hole five feet across will depressurize a jetliner in a fraction of a second. Pounds-force per square inch (lbf/in²) is a non-SI unit of pressure. ... A millibar (mbar, also mb) is 1/1000th of a bar, a unit for measurement of pressure. ... HPA means Physiology Hypothalamic-Pituitary-Adrenal axis: The hypothalamus, pituitary and adrenal glands work together to regulate hormone levels and maintain homeostasis. ... It has been suggested that this article or section be merged with Sound barrier. ...

Rapid decompression of commercial aircraft is extremely rare, but dangerous. People directly next to a very large hole may be blown out or injured by flying debris. Floors and internal panels may deform. Hypoxia will result in loss of consciousness without emergency oxygen. Onset of hypoxia-induced unconsciousness varies depending on the altitude:

Additionally, the air temperature will plummet due to expansion, potentially resulting in frostbite. Frostbite (congelatio in medical terminology) is the medical condition where damage is caused to skin and other tissues due to extreme cold. ...

• Contrary to Hollywood myth, people just a few feet from the hole are more at risk from hypoxia than from being sucked out.
• Contrary to Hollywood myth, a bullet hole in a window, or even the loss of an entire passenger window, will not cause explosive decompression. This was demonstrated on MythBusters.

Explosive decompression (ED) is a sudden drop in pressure that occurs in 0. ... MythBusters is an American science television program on Discovery Channel starring special effects experts Adam Savage and Jamie Hyneman, who set out to test the validity of myths and urban legends of popular culture. ...

Effects of cabin pressurization on an aircraft fuselage

As the airplane is pressurized and depressurized, the metal skin of the airplane expands and contracts, resulting in metal fatigue. Modern aircraft are designed to resist this compression cycle, but some early jetliners (see De Havilland Comet) had fatal accidents due to underdesign for fatigue. Metal Fatigue is a 1999 real-time strategy and mecha computer game developed by Zono, Inc and released by Psygnosis. ... The de Havilland Comet of Britain was the worlds first commercial jet airliner. ...

Effects of cabin pressurization on the human body

• Ear and paranasal sinuses - One needs to adjust to the pressurized cabin air from the beginning. 1 in 3 passengers suffer ear discomfort, pain and temporary hearing loss on takeoff or landing, called "aerotitus" by the House Ear Institute in Los Angeles. Rapid changes in air pressure cause the air pocket inside the ear to expand during takeoff and contract during descent, stretching the eardrum. To equalize pressure, air must enter or escape through the Eustachian tube. "If a passenger has serious congestion, they risk ear drum damage", says Sigfrid Soli, Ph.D., head of the HCSD Department at the HSI(?).
• Tooth - Anyone with intestinal gas or gas trapped in an infected tooth may also experience Barodontalgia, a toothache provoked by exposure to changing atmospheric pressure.
• Pneumothorax - Anyone who has suffered a pneumothorax is recommended not to fly (even in a pressurised cabin) for at least 1 month and should obtain an x-ray prior to travelling.

As well as the more acute health effects experienced by some people, the cabin pressure altitude of 8,000 feet typical in most airliners contributes to the fatigue experienced in long flights. The in-development Boeing 787 airliner will feature pressuration to the equivalent of 6,000 feet, which Boeing claims will substantially increase passenger comfort. A human ear (also called auricle or pinna) The ear is the sense organ that detects sound. ... The paranasal sinuses are eight (four pairs) air-filled spaces, or sinuses, within the bones of the skull and face. ... Category: ... Flag Seal Nickname: City of Angels Location Location within Los Angeles County in the state of California Coordinates , Government State County California Los Angeles County Mayor Antonio Villaraigosa (D) Geographical characteristics Area     City 1,290. ... The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... Anatomy of the human ear. ... Doctor of Philosophy (Ph. ... HSI, a Three-Letter Acronym meaning: Hang Seng Index Horizontal Situation Indicator; similar to a CDI; an instrument used to determine aircraft position relative to a naviation aid, or to fly TO or FROM a navigation aid. ... This article or section does not cite its references or sources. ... In medicine (pulmonology), a pneumothorax or collapsed lung is a medical emergency caused by the collapse of the lung within the chest cavity. ... The Boeing 787 Dreamliner is a mid-sized wide body passenger airliner currently under development by Boeing Commercial Airplanes and scheduled to enter service in 2008. ...

Some people may still experience symptoms of altitude sickness despite the cabin pressure. Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by lack of adaptation to high altitudes. ...

Noted incidents

• Golfer Payne Stewart died in an aircraft accident as a result of loss of cabin pressure.
• Helios Airways Flight 522, a Cypriot Boeing 737, crashed in Greece on August 14, 2005, killing all 121 people on board. It is currently believed that the plane depressurized and the pilots fell unconscious.

Payne Stewart on the cover of the 2001 paperback edition of the authorised biography by Tracey Stewart with Ken Abraham. ... Airbus A380 An aircraft is any machine capable of atmospheric flight. ... A railing accidentally collapses at a college football game, spilling fans onto the sidelines An accident is something going wrong unexpectedly. ... Helios Airways is an airline operating scheduled and charter flights from Larnaca and Paphos in Cyprus. ... Helios Airways Flight 522 (HCY 522 or ZU522) was a Helios Airways Boeing 737-31S flight that crashed on August 14, 2005 at 12:04 EEST into a mountain north of Marathon and Varnavas, Greece. ... The Boeing 737 is the worlds most popular medium range - narrow body commercial passenger jet aircraft. ... August 14 is the 226th day of the year in the Gregorian Calendar (227th in leap years), with 139 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

See also

• Atmosphere (unit)
• Bleed air
• Explosive decompression
• Gas compressor
• Rarefaction
• Spacesuit

When expressed as a measurement, an atmosphere (symbol: atm) or standard atmosphere is a unit of pressure roughly equal to the average atmospheric pressure at sea level on Earth. ... Bleed air in jet turbines is compressed air taken from within the engine, after the compressor stage(s) and before the fuel is injected in the burners. ... Explosive decompression (ED) is a sudden drop in pressure that occurs in 0. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ... Rarefaction is the reduction of a mediums density, or the opposite of compression. ... Apollo 15 space suit A spacesuit is a complex system of garments, equipment, and environmental systems designed to keep a person alive and comfortable in the harsh environment of outer space. ...

References

1. ^ K. Baillie and A. Simpson. Altitude oxygen calculator. Retrieved on 2006-08-13. - Online interactive altitude oxygen calculator

• Portions from the United States Naval Flight Surgeon's Manual
• CNN: 121 Dead in Greek Air Crash
• "Explosive Decompression" segment of MythBusters episode 10, January 11, 2004
  • also shown as a segment of Beyond Tomorrow episode 12