| | | This Paul Leppin article was posted 2 months ago. That would have been after the completion of amendment 3 and about the time amendment 4 was implemented...
HEPA filters for airliner cabins: State of the art and future development The authors used BS EN 1822-2009 with a transition duct recommended by ASHRAE Standard 52.2 to evaluate the performance of various filters used on Airbus and Boeing aircraft, including those still in operation (e.g. B737, B777, B787, A320, A330, and A380). The authors found that the filtration efficiency ranged from 99.46% to 99.99% in aircraft that are still being used. This shouldn't be surprising given the fact that OEMs ensure that the filter manufacturers meet their specifications. However, the use of high efficiency filters comes with a price. These HEPA filters have an extremely high pressure drop (134 to 412 Pa). This, in turn, increases fuel burn as the recirculating fans have to work hard to drive the required airflow through the filter and back to the aircraft cabin. To reduce the pressure drop, the authors suggested the use of nanofiber media to replace glass fiber media. In their tests, the authors tests found that the filter material change pressure drop was reduced from 84.7 Pa/(cm/s) to less than 28.5 Pa/(cm/s). There are some challenges to using nanofiber media as it would need to formulated to ensure they do not post a fire and smoke risk.
The authors did note that the most penetrating particle size (MPPS) tends to decrease with these new filter media, which may require new performance testing methods. Also, they cited past work that found that the peak size of particles in the airport environment is around 0.1 microns -- a size that current testing methods do not cover. This is a rather curious given that the SARS-CoV-2 virus measures about the same size. However, I wouldn't expect to see much of a difference in filter performance if these filters are tested down to this size but perhaps it should be investigated if only to close this knowledge gap. |
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