With my typical enthusiasm over-riding caution, I started to plot filter efficiency of common filters (calculated from published Beta Ratios), to see if I could come to some price per quality conclusions. I "published" the preliminary and got hammered on my use of the Beta Ratios to calculate filter element efficiency. I am taking this to you, as you are more technical, to either validate, or (gently) correct my methodology.

Here an example of what I am doing, please correct. From the Wix on-line catalog, I look up the Beta's of filters of interest and do the following calculations:

Wix P/N 51515; B2/20 = 13/23; 50% @ 13µ ; 95% @ 23µ
Wix P/N 51068; B2/20 = 10/26; 50% @ 10µ ; 95% @ 26µ
Wix P/N 51367; B2/20 = 12/24; 50% @ 12µ ; 95% @ 24µ

From what I understand and a quick call to Wix to verify their #51515, it looks like you're on the right track. I would imagine that Wix is using J1858 for multi-pass efficiency.

Regards,
paul....

thanks!

based on this and other examples, it appears that the ISO standard did not standardize nomenclature, or people ignore it. I see "Bx = y" interchanging what x and y mean (micron size vs. Beta Ratio) in various vendor literature. I have learned to look for a pattern of either "2" or "divisible by 5" to decide on if x or y is the "Beta."