How Do Aircraft Supply Breathable Air?

When travelling from sea level to higher altitudes, some may have experienced altitude sickness caused by “low levels of oxygen”. Contrary to this popular belief, even high altitudes have plenty of oxygen available in the air. The real culprit is the low pressure of the air which leads to an inability for the oxygen to permeate into our circulatory system, due to the fact that our lungs must have lower air pressure than the outside air. When flying, it is important that there is ample breathable air in aircraft for both the cabin and crew to be healthy and comfortable. In this article, we will discuss how aircraft have been designed to supply air at a pressure and temperature that we rely on for safe and comfortable travel.

Before modern aircraft design and with the discovery that high altitudes would cause loss of consciousness, pilots often utilized masks that supplied pressurized oxygen from tanks for safe flight. This, however, could not be feasible for an entire crew or passengers to have to rely on. In the 1930’s, the US Army Air Corps researched and developed pressurized cabins which then led to the further development of modern aircraft oxygen supply that does not rely on masks or tanks. This is achieved through the pressurization of bleed air that is captured and compressed through the engine turbines of the aircraft.

As the aircraft is in flight, air enters the jet engine turbine and is compressed by the fan blades. Air continuously heats and compresses until it is diverted for various functions including fuel combustion, deicing components, and cabin oxygen supply. The hot air for the cabin is then diverted through intercoolers and air pacts before passing into an expansion turbine, all working together to cool the air to a comfortable level. From there, the air is then vented into the cabin for the passengers. In the aircraft, pressurization and air quality is regulated through the use of pressure sensors and an outflow valve that removes old air from the aircraft.

Cabin pressure controllers also act as a very important component to the air quality and pressurization as they allow for the control of the outflow valve. With the controller, the pressurization of the cabin can be manipulated and slowed down to a comfortable rate as the aircraft climbs. While the aircraft may have a rate of climb anywhere from 1500 to 2000 feet per minute depending on the stage of climb, the controller allows for a slower relative rate of climb pressure change in the cabin which lies around 20% of actual ascension, allowing for a more mild change in pressure for the passengers. Through these technologies, passengers and crew can experience a safe and comfortable flight with ample breathable air.

At Aviation Orbit, owned and operated by ASAP Semiconductor, we can help you find emergency oxygen masks you need, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. For a quick and competitive quote, email us at or call us at +1-509-449-7700.


December 7, 2023
June 30, 2022

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