Article originally published on Noria.com
"My filter company uses the following notation to rate one of its filters: BX=2, B10=X, BX=75, followed by these numbers: 5, 8 and 17. I'm familiar with the Beta rating, but I've never seen it shown in this way. What is meant by these numbers?"
This system of rating a filter describes its capture efficiency at three specific points in microns. It actually has many advantages over the more common Beta rating methods used today.