This is the first controlled demonstration that mechanical filtration at MERV 14 prevented aerosol transmission of PRRSV. It used a dual chamber model, with infected and susceptible populations separated by the filtration system under test. The result established the proof of concept on which barn filtration is built.
Everything that followed rests on it. Dee and colleagues moved from chamber to herds in 2012 and reported odds of new infection 7.97 times higher before filtration than after across 38 herds. Alonso and colleagues reported an approximately 80 percent reduction in the risk of novel introduction in 2013. Desrosiers and Cousin assembled 65 filtered farms in 2023 and found 95.4 percent remained PRRSV negative. The same group's field sampling work established the long distance transport this filtration is defending against, at 4.7 kilometres in 2009 and 9.1 kilometres in 2010.
MERV 14 became the reference minimum from this study, and two qualifications belong with it. MERV is ASHRAE 52.2, a North American scheme that is not interchangeable with the EN 779 or ISO 16890 classes used in the European literature, so a class number quoted without its scheme is ambiguous. And a MERV rating describes a filter on a test bench when new, which the field work on charged media by Raynor and Chae and by Osborne shows is not always what the same filter delivers in service. The rating is the starting point for a specification rather than the whole of it.