There is a significant economic advantage to maintaining a PRRS negative herd, whether it is a boar stud, sow farm, or nursery-grow-finish. As the reality of aerosol transmission of PRRS, Swine Influenza, and Mycoplasma are being more accepted, any means to prevent aerosol transmission of these agents is of great interest. Our practice has taken an aggressive approach with our producers on air filtration systems. Six farms implemented filtration in 2005, five in 2006, eleven in 2007, and eleven in 2008. An important consideration for us from the start has been that we shouldn’t expect to never have a PRRS break just because we installed air filtration. However, if we can reduce the incidence of PRRS breaks significantly, it would be good return on the investment.