Pre-Filter with ShieldThe Pre-Filter system (PF 040 and PF Shield) provides a way to filter out some of the excess debris that may have been collected during the sampling process.  It conditions the sample by trapping and removing the debris that is larger than 40 microns.  It is done prior to concentrating the collected sample through the concentration filter (Filter 100).  Granted, there is some risk of trapping some of the viable target cells amid the debris, but for samples where the debris may cause downstream processing problems, it is available as a sample conditioning method.