Comparison of Filtration Efficiency Measurements between TSI Model 8160 , TSI Model 3140 , and ATI 100 P Filter Test Stands

The penetration result obtained on a filter test stand depends on several factors. Two of these are challenge aerosol size distribution and the particle detector used to measure the particle size and concentration. Some filter testers employ a monodisperse aerosol challenge while others use a polydisperse challenge. Some particle detectors are based on particle counting while others are based on light scattering detection. Johnson and Smith have shown that small differences in these factors can have a dramatic effect on the penetration value obtained. Other factors that affect the penetration are the fiber diameters in the filter media tested and the face velocity of the test. The goal of this study was to present a correlation between the MPPS penetration as measured by the TSI CertiTest 8160 and the penetration values obtained by the TSI model 3140. We also present a correlation of MPPS penetration with filter media face velocity that may be useful for extrapolation purposes. For the HEPA and sub-HEPA grades the 100P penetration was measured to estimate the particle size this test stand is measuring compared to the 8160. Introduction The age of high efficiency filtration began after WWI when protection of troops from poisonous gas attacks became a priority for the military. In the area of filter testing, LaMer and Sinclair developed a filter test stand using a thermally generated di-octyl-phthalate (DOP) smoke cloud to challenge the filter and optical photometers to determine aerosol concentration upstream and downstream of the filter. At that time the DOP smoke was thought to be an aerosol of monodisperse 0.30 micrometer spheres. This instrument became the basis for US MIL-STD-282 and subsequently MIL-STD-51079 and MIL-STD51068 for testing HEPA filter media and HEPA filters. Later Hinds et al determined that the hot DOP aerosol generated by the Sinclair test stand was not monodisperse, but was actually a polydisperse aerosol having a count mean diameter of 0.23 micrometers. Even so, MIL-STD-282 has remained the accepted industry standard for testing HEPA filter media. In recent years ATI has developed a cold DOP aerosol test stand, model 100P, to replace the Q-127 thermal DOP test stand. ATI reports that the cold DOP aerosol generated by the 100P has a count mean diameter of 0.22 micrometers and geometric standard deviation of 1.6. With the introduction of filter test stands based on laser particle counters and condensation particle counters combined with differential mobility particle sizers in the 1980’s, new filter efficiency test stands were developed to meet the needs of the booming electronics industry. The newer particle counter based test stands could accurately measure filter efficiencies of up to 99.999998 percent on particles ranging in size from 0.075 to 10 micrometers for laser particle counters and 0.015 to 0.40 micrometers for condensation particle counters. These test stands allowed the generation of fractional penetration curves that experimentally demonstrated Langmuir’s theory that there is a particle size for which filtration efficiency of a filter medium is minimum. Two standards that reference reporting the penetration at the most penetrating particle size (MPPS) are IEST-RP-021 and the European standard, EN1822. The CertiTest 8160 is a filtration test stand that utilizes monodisperse challenge aerosol and condensation particle counters (CPC’s) to detect the aerosol concentration upstream and downstream. This filter tester has the capability of measuring a fractional penetration curve for particle sizes in the range of 0.015 to 0.4 micrometers. The Model 3140 is a new generation of TSI 8140 tester. It is also a CPC based filtration test stand, but only provides a single penetration measurement for a fixed particle size distribution aerosol challenge.