This laboratory study tested four filter prototypes against PRRSV, equine arteritis virus, bovine enterovirus, Actinobacillus pleuropneumoniae and Staphylococcus aureus. Bacterial reduction reached up to 99.9 percent and viral reduction was approximately 98 percent. The most effective arrangement was a prefilter combined with a fiberglass secondary filter. PRRSV infectivity within the filter fell below detection at 24 hours, while S. aureus remained culturable at four weeks. The prefilter and fiberglass combination was tested at 1,800 cubic metres per hour and the filter mat prototypes at 80 cubic metres per hour.
The survival difference between the virus and the bacterium is the finding with the longest reach. A filter is not only a barrier but also a surface holding what it has captured, and how long that material stays viable determines what handling a filter change requires. Four weeks of culturable S. aureus on media is a different maintenance proposition from a virus below detection within a day.
One caveat governs how the specifications can be quoted. The paper classifies its filters in EN 779 terms, using EU class G4 for the prefilter and EU class F9 for the fiberglass secondary, with filter mats at M6 and F8 to F9. EN 779 was fully withdrawn on 1 July 2018 and replaced by ISO 16890, and no exact conversion exists between the two schemes because the test methods differ. Those class designations should only ever be reproduced with the standard and year attached, and never silently restated as an ePM equivalent or as a MERV number.