Summary
This Vis Filter is a specialized conduit that slowly draws out any tainted vis flowing through it and pumps it directly into the atmosphere. This process occurs relatively slowly, but if a proper and constant flow is maintained through the filter it is possible to rid ones conduit network of any unwanted taint. Of course, the taint does end up messing with your aura, but such is the cost of progress.
It is possible to stack additional filters on top of each other. Only the bottom-most filter can connect to other conduits, but each additional filter in the stack reduces the amount of taint that gets pumped into the atmosphere - some of the taint is simply destroyed. This does slow the filtering process down however, but it is much kinder to the environment.
Filters draws taint them at a strength of 15 TCB.
Craft
Source - Thaumcraft2 Wiki