Removal of ultrafine particles in indoor air: Performance of various portable air cleaner technologies

Ultrafine particle (UFP) exposures have been associated with human morbidity and mortality. The removal of UFP from indoor air using portable air cleaners (PACs) of various technologies has not been studied in detail. In this study, 12 devices representing different PAC technologies were tested with an UFP challenge in a full-scale stainless-steel chamber. UFP generation and measurements were conducted using a six-jet atomizer and scanning mobility particle sizer, (SMPS) respectively. It was found that high-efficiency particulate air (HEPA) and electrostatic precipitator (ESP) PACs have the best performance in terms of UFP removal rate, with an electret-based PAC also showing comparably high removal rates. Using modeling based on the experimental findings, some PAC technologies were shown to be effective in reducing indoor UFP concentrations in a typical Quebec City residential room by a factor of about 90%. Negative and bi-polar ion generators were found to have mediocre UFP removal performance, while photocatalytic oxidation-, ozone generation- and ultraviolet germicidal irradiation (UVGI)-based PACs had very limited or no UFP removal capabilities. Estimates of costs per performance index (Capital + Operating Costs/Calculated Clean Air Delivery RateCADR) showed that the HEPA-1, ESP- and electrets (FEF) based PACs provided the highest value for money in terms of total UFP removal performance.