Originally Posted by Farnsworth
That's very high efficiency, single pass at 8-10 microns. Must be the best ever. It's easier to understand single pass I think than multi. Essentially it become 100% at 8-10 very quickly. The one big inlet hole identifies it as Champ Labs.
The multi-pass test is basically a continuous single past test repeated over and over since they use a particle counter bith up stream and down stream to monitor instantaneous efficiency across the filter. So at any given time during the multi-pass efficiency test they can essentially get "snap-shot" data of the single pass efficiency through the media.
The advantage of the multi-pass test is that it also measures holding capacity and defines the delta-p curve as the filter loads up, and also gives data that shows if the filter's efficiency changes with loading. It's a more valuable test compared to a single pass test.
When someome advertisers a single pass efficiency It's most likely at a test point shortly after the test starts, ie, the efficiency of a new unloaded filter. As seen, loading of oil filters with debris does not necessarily mean they get more efficient, because increased delra-p can cause trapped particles to dislodge and decrease down stream efficiency.