As more attention is put on health, safety and sanitation, many aircraft owners are starting to look closer at what’s inside their aircraft. Maybe more importantly, they want to know what’s kept out. With different manufacturers advertising different air filtration systems and touting certain systems as better than others, being an educated buyer is imperative.
The following information is intended to help you become more aware of terminology and assist in your understanding of the potential systems in your aircraft.
FRESH AIR SYSTEM
Aircraft that include a “fresh air system” focus solely on circulating fresh air from outside of the aircraft into the cabin. Because the air coming into the cabin is consistently “fresh” from outside, there is no recirculation and therefore, no need for an additional filter. Aircraft with this type of system do not have a dedicated recirculation system apart from air conditioning evaporators. One full volume exchange varies between aircraft but typically takes two minutes or less.
The Process:
1. Air enters the aircraft from outside
2. Air is compressed and heated by the engine, killing germs, bacteria and viruses
3. Air is cooled to cabin temperature
4. Air enters the cabin through distribution ducting
5. Air exits the aircraft at the aft through outflow valves
PARTIAL RECIRCULATION SYSTEM
Aircraft that include a “partial recirculation system” reuse a percentage of air from the cabin while also relying on fresh air to fill the cabin. These systems use HEPA (High-Efficiency Particle Arrestance) filters, which consist of a cluster of fibers that filter out pathogens, dust and other contaminations as air is forced through. One full volume exchange varies between aircraft but typically takes four minutes or less.
The Process:
1. Air enters the aircraft from outside
2. Air is compressed and heated by the engine, killing germs, bacteria and viruses
3. Air is cooled to cabin temperature
4. Air enters the cabin through distribution ducting
5. Air exits the aircraft at the aft through outflow valves
6. Small percentage of air does not exit the aircraft and is pushed through a HEPA filter
7. Recirculated air mixes with fresh air and enters the cabin
IONIZATION SYSTEM
Aircraft with an “ionization system” include a component that is mounted onto the air duct and works electronically to remove germs and viruses present in the cabin. Depending on the system, this can be installed in the aircraft permanently or be carried onto the aircraft and used.
The Process:
1. Electronic system produces positive and negative ions from hydrogen and oxygen molecules in the water vapor in the air
2. Ions cluster around germs, odors and other particles in the cabin air
3. Natural reaction deactivates pathogens and makes odors dissipate
WHICH SYSTEM IS THE BEST?
Determining which system is best comes down to personal preference. No system is proven to be more effective than another. Because some of these systems are tied to the overall design of the aircraft, systems are often not easily interchangeable and have reasons for why they were selected and put in place.
When exploring filtration systems, focus on your mission and your reason for joining the world of general aviation. Once you’ve found the right aircraft, explore the filtration system and be educated about what will, and will not be inside your cabin. Rest assured, each of the filtration systems discussed has measures in place to keep harmful germs and pathogens away from your cabin.
Here are some easy questions to ask your manufacturer when exploring specific aircraft.
1. How much time does it take this aircraft’s system to complete one full volume exchange?
2. How will the filtration system affect the interior materials and fabrics?
3. Why does this specific system work best on this aircraft?
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