For most commercial aircraft, operations are carried out at an average altitude of around 33,000 to 42,000 feet above sea level. At this height, modern engines can perform optimally and with the benefit of avoiding common adverse meteorological conditions. Despite these advantages, oxygen conditions at such heights are not suitable for breathing, making it essential that passengers, pilots, and crewmembers are offered an atmosphere that is safe and comfortable. To do this, cabins are sealed, pressurized, and supplied with a stream of breathable air. In this blog, we will discuss the process of air circulation for commercial aircraft, allowing you to better understand how such environments are established and upheld.
When flying on a commercial aircraft, around 60% of the air you breathe is fresh, while the remaining 40% is recycled. While fresh air is supplied by systems that draw, condition, and pressurize atmospheric air, recycled air runs through a number of HEPA filtration systems to be reused. These HEPA filtering systems are comparable to those found in hospital theater rooms, featuring advanced pores capable of trapping dust and other contaminant particles from airflow. These filters can even remove bacteria and viruses, boasting a trapping efficiency rate of around 99.7% on average.
As contaminants may vary in size, HEPA filters take advantage of a number of capturing elements and removal methods. For example, filters are designed to have pores small enough to capture particles around 0.3 to 10 microns in size. Additionally, filters may even utilize the concept of magnetic attraction to draw particles onto the sides of filter pores. For the smallest particles that are smaller than 0.2 microns, Brownian motion is relied on to cause contaminants to collide with one another before becoming trapped on fiber walls. Through this entire process, air can be filtered to a clean and safe state for reuse. To further ensure the cleanliness of breathable oxygen, the average aircraft cabin will have filtration occur every 2 to 3 minutes. While recycling air can allow for ventilation costs to be reduced, there is also the added benefit of managing fluctuating temperatures. Atmospheric air will generally be extremely cold, making it important that internal climates are governed for safety and general comfort.
In terms of fresh air, oxygen is supplied by the engine as it captures atmospheric air through intakes. While much of this air is compressed and mixed with fuel for combustion, some of the compressed air is directed to condition packs to lower temperatures for breathability. With a mixing fold and ducts, the stream of fresh oxygen can be combined with recycled air before being vented into the cabin. To best ensure cleanliness through venting, air is directed downward, directly at passengers.
With a better understanding of cabin air systems, you can have more knowledge on how commercial aircraft operations are carried out while keeping all individuals on board comfortable and safe. Like many other aircraft components, filters, inlets, ducts, aircraft coolers, and other such equipment will all necessitate regular inspection and replacement to ensure proper functions. If you are conducting maintenance and find that you require parts for repair or replacement, let the experts at Veritable Aviation help you source all you need with competitive pricing and rapid lead times for your benefit.
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