In air filtration, for creating healthy indoor air, there is an intrinsic conflict between high filtration efficiency and low wind pressure drop. In this study, we overcame this conflict by developing new dielectric heterocaking (HC) filters, in which high relative dielectric constant (εr) materials were heterogeneously loaded on traditional polymer fibers. The dielectric HC filters in an electrostatic polarizing field generate a great amount of charges on their surface, leading to a strong attraction to precharged aerosol particles, and result in high filtration efficiency. Observing via a charged coupled device camera, the migration speed of aerosol smoke particles toward the polarized HC fiber exceeded those toward the unpolarized HC fiber by a factor of 6. We loaded high-εr HCs including manganese dioxide (MnO2), activated carbon, zinc oxide (ZnO), copper oxide (CuO), and barium titanate (BaTiO3) on polyurethane foams using a fast and large-scale roll-to-roll gel squeezing method. Based on the experimental results, when HCs had a εr larger than 5.1, an increased εr did not benefit electrostatic filtration efficiency for aerosol particles much, but resulted in a larger net ozone production. We suggested a MnO2-HC filter for efficient and multifunctional filtration of indoor particles, ambient ozone, and formaldehyde with only 3.8 Pa pressure drop at 1.1 m/s filtration velocity. This efficient and cost-effective dielectric HC filter opens a new avenue for the design of multifunctional filters, which will facilitate its large-scale production and commercial application in the ventilation system for healthy buildings.

Three-dimensional (3D) printers using the fused filament fabrication technique are in widespread use, and they are known to emit ultrafine particles (UFPs) and volatile organic compounds (VOCs). This fact raises concerns due to their impact on indoor air quality and human health. Several emission control measures have been previously proposed but without being confirmed in the near real-life situation. In this study, the effectiveness of the control measures in reducing the UFPs and VOCs was tested in a standardized 30 m 3 environmental test chamber. We found that a filter cover and an air purifier were effective in removing 74−93% of UFPs, with the filter cover providing the best UFP filtration. Control at the source location seems to be more efficient than trying to remove particles following their emission. However, the control measures showed varying abilities to remove major VOCs of styrene and ethylbenzene. Moreover, new VOCs were emitted from the use of control devices. After the newly opened filters had been conditioned and the control devices had been operated for 4−5 days, the VOC emissions decreased. The study shows the necessity of further studies of VOC control measures, which should preferably have efficient and consistent removal ability, as well as minimal emissions.

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