Aircraft Air Filtration Systems

Aircraft Air Filtration Systems

True High-Efficiency Particle Filters (True HEPA) or High-Efficiency Particle Filters (HEPA).

These filtration systems then filter and recirculate the air from the cabin and mix it with fresh air. The dirtier a HEPA filter gets, the more efficient it becomes, so it can easily handle the passenger load, even on larger jets.

Air recirculation also happens pretty quickly. The HEPA filtration system can make a complete air change approximately 15 to 30 times per hour, or once every two to four minutes. According to IATA, the International Air Transport Association, "HEPA filters are effective at capturing greater than 99 percent of the airborne microbes in the filtered air. Filtered, recirculated air provides higher cabin humidity levels and lower particulate levels than 100 percent outside air systems."

HEPA filters catch most airborne particles, meaning their capture standard is pretty high in terms of commercial spaces.

These filters only treat the recirculated air so some particulate contamination, odor causing compounds and volatile and semi-volatile organic compounds (VOCs and SVOCs) may enter from the outside air system. Air purification systems that treat both the outside air ('bleed air') and the recirculated air are in development.

Modern Cabin Air Filters remove particles throughout the spectrum of sizes which are found in the aircraft cabins. There are three primary methods by which a filter removes particulate, and all three mechanisms are in operation in fine air filters. The three mechanisms are “Direct Interception,” “Inertial Impaction,” and “Diffusional Interception”:

Due to the large number of passengers in the aircraft cabin, there may be high concentrations of dust, fibers, bacteria, and other microorganisms. All of these are nuisances and potential health hazards to crews and passengers. In order to enhance passenger and crew health and comfort, HEPA filters must be fine enough to control these contaminants.

Sources:

https://www.iata.org/contentassets/f1163430bba94512a583eb6d6b24aa56/cabin-air-quality.pdf

https://www.skybrary.aero/index.php/Cabin_Air_Quality_and_Contamination

https://aerospace.pall.com/en/commercial-fixed-wing/how-cabin-air-systems-work.html