here's another more recente presentation on swinehttps://www.pork.org/filelibrary/2011%20Swine%20Education%20In-Service/Filtration%20-%20Steve%20Pohl.pdf
Three major vendors indetified on slide 4: Camfill Farr, Clarcor and Noveko.
Air filtration cost for such big farming installation can be found on slide 62.
By the way, Monitrol offices are located in Boucherville right next to highway 20, they are the ones distributing our air filters for the farm industry.
Delmic