Reducing particle exposures in a tropical office building using electrostatic precipitators

Epidemiological surveys have shown that indoor fine particle exposures are associated with various health outcomes. Concomitantly, empirical data on the impact of electrostatic precipitation filter use on indoor particles in an office building has not been published. This research reports an intervention study on the impact of various filters within the air-handling unit (AHU) of a tropical office building. The following filtration methods were tested: (1) media filters (MED); (2) electrostatic precipitation filters (EAC); and (3) electrostatic precipitation filters enhanced with a media pre-filter (EAC-PF). The efficiencies of EAC filters were significantly superior to media filters for the removal of fine particles. Enhancement of EAC with media pre-filters (PF) augments the fine particle removal resulting in overall efficiencies comparable to that of HEPA filters. However, there was no difference in the removal efficiencies of coarse particles between MED, EAC and EAC-PF filters. When indoor particle removal effectiveness was evaluated, EAC and EAC-PF filters were more effective than MED filters for submicron particles. Further, effectiveness of EAC-PF was significantly superior to EAC due to effects of PF filtration of large particles, backpressure and lesser re-entrainment of large particles into the supply air stream. Effectiveness of EAC and EAC-PF were lower in occupied compared to non-occupied periods due to the higher particle loadings on collection plates. Using mass balance models, the results showed that effectiveness of electrostatic precipitation filters will improve as recirculation rates increase. These findings suggest that employing electrostatic precipitator filters under high recirculation rates can be an energy efficient strategy to reduce harmful indoor fine particle exposures.