Influence of Filter Fiber Material on Removal of Ultrafine and Submicron Particles Using Carbon Fiber Ionizer-Assisted Intermediate Air Filters
Journal article, 2012
Ultrafine and submicron particles are possibly highly related with respiratory and cardiopulmonary diseases and syndromes. Many studies show that an ionizer operated upstream of a ventilation air filter could enhance the particle collection efficiency of the filter, without affecting the pressure drop. However, most of these studies are based on one single fiber material and does not develop any comparison among different ventilation filters. This study investigates the influence of the fiber material and filter class on the enhanced efficiency. The influence of ion concentration is also considered. The experiments were conducted in a full-scale filter test rig and a chamber with 100% air re-circulation. Seven ventilation filters of class F5-F9 (MERV11-15), made of three types of fiber materials were tested in the filter test rig. A Scanning Mobility Particle Sizer (SMPS) was utilized to count ultrafine and submicron particles in the upstream and downstream air flow. In the chamber test, a charged synthetic filter of class G4 (MERV 8) was mounted in the air re-circulation system. A P-TRAK Ultrafine Particle Counter, a CI-500 optical particle counter and a Dust-TRAK Aerosol Monitor were used to measure ultrafine and submicron particles. The results show, under the given experimental conditions, that ionization could substantially improve the filtration efficiency. For example, assisted by the ionizer, the coarse G4 (MERV 8) filter showed a filtration efficiency that increased by about 30 to 40 %-units for submicron particles. For the same ion concentration, the enhanced efficiency of charged synthetic filters is higher than that of glass fiber filters, especially in the ultrafine particle size fraction. Similarly, with the same ion concentration, the charged synthetic filters of higher class showed higher enhanced efficiencies than the charged synthetic filters of lower class. Measurements showed a negligible generation of ozone, both in the filter test rig and in the test chamber experiments.