What are the body's filters?

Static charges any different between HEPA and "passive" Washable electrostatic filters?

• I'm still doing my research on "passive" air filters (i.e. those not applied any electric current) and I know that what are being referred to as washable "passive" electrostatic media filters are supposed to generate a charge (that attracts particles) following the friction resulting from air passing through the media. My question is that, is this "charge" any different from what would also occur from ordinary glass or synthetic (polypropylene) HEPA media filters? Air friction goes through the HEPA filters as well (in fact, more so given the additional resistance), so would they not also be expected to generate electrostatic charges on their surface media similar to what is expected of passive electrostatic media filters? An additional question is that is it true that each time you wash a passive electrostatic filter with water, that the surface charge dissipates (given the effects of the water to neutralize the charge) and thus the charge must be "re-generated" following air friction upon re-usage? Thanks,

• Answer:

  HEPA Filters (that do not specify an electrostatic function) stop particles by the size of the mesh/filter elements. In a high-particle environment, they will clog quickly. Their materials are not designed to create static charges based on the passing air - so they do not function the same way. Passive electrostatics rely on the friction of the passing air to generate the static charges - cleaning them does not change the materials (and the materials are chosen for that purpose and function) so that the function does not degrade over time. They will wear out, but that is a separate issue. Some filters do both - generally at a higher cost and requiring more frequent cleaning.