Photometers or Particle Counters for Filter Testing? 

This presentation describes the benefits of testing HEPA/ULPA filters installed in clean air and containment facilities with the Photometer method described in ISO14644-3.
It is true that there are applications where the particle counter is better, because of the air and surface chemistry risks of using oil aerosol particles in a high-tech cleanroom, but for every installed filter the easiest, fastest and most reliable method is with a Photometer.