I wish we could get a final answer on what rating these filters are at..
In any case, but this stuff into perspective. Lets say that it only filters down to 10um.
Put into perspective, 10 Micron =
"Microbes are dispersed from skin cells, and a human body sheds the outermost layer of skin every 24 hours.
1 BILLION SKIN FLAKES EVERY 24 HOURS.
A skin flake is typically 33 microns - 44 microns. They break down to typically 20µ (micron) but 7-10% are less than 10µ (micron). The equivalent diameter of bacteria carrying particles is 12-14µ (micron). These settle by gravity at 0.37 meters per second."
12-14µ (micron) size particles will settle in wounds of hospital patients and aseptically filled containers in pharmaceutical applications by gravity."
http://www.mvent.com.ph/references/cleanroom.htm
Or:
Beach Sand 100 to 2000 microns
Human Hair 40 to 300 microns
Mold Spores 10 to 30 microns
Pollens 10 to 1000 microns
Fertilizer 10 to 1000 microns
http://www.lakeair.com/index-2_b.htm
Which is a point that I made a long time ago.. While many bypass filters may filter to a finer micron then 10um, the actual benefit to cost isn't enough to justify it.
Or, put another way: at what point is enough filtration enough, and how do you determine it? Why stop at 2-3 micron in size? Why stop at .1 micron in size? Where does it end and why?
(Thats a general question to anyone who wants to answer)