FILTER PENETRATION MEASUREMENTS USING A CONDENSATION NUCLEI COUNTER AND AN AEROSOL PHOTOMETER

We conducted both theoretical and experimental comparisons of two instruments, a condensation nuclei counter and an aerosol light-scattering photometer, to determine how they measured the penetration of high-efficiency particulate air (HEPA) filters. In some experiments we simulated leaks around the test filter to ascertain how such leaks affect the two instruments' penetration measurements. Results of all of the experiments indicate that differences in the measurements vary widely from no difference to a factor of 10. These variations are related to certain functions that depend on particle size: the response function of the photometer, the filter penetration, and the distribution of the test aerosol.