In-duct electrostatic air filters (ESP) have been shown to be an effective particulate control device for reducing UFP concentrations (20 nm - 100 nm) in buildings, although they have the potential to increase indoor ozone concentrations due to corona discharge. This study investigated using residential ESP filters to reduce ultrafine particles between 4 nm to 15 nm, and quantified the resulting ozone generation. In-duct ESPs were installed and operated in the central air handling unit of a manufactured test house. Results for the two tested ESP brands indicate that removal efficiency of 8 nm to 14 nm particles was less than 10 %, possibly due to low charging efficiency for these sized particles. Adding a media filter downstream of the ESP increased the removal efficacy to up to 27 % for particles in the same size range. Continuous operation tested ESPs in the unfurnished house raised indoor ozone concentrations by 20 ppbv to 77 ppbv,. Extrapolating the ozone concentrations to other houses is complicated as the concentrations are highly dependent up on HVAC duty cycle and ozone reactivity of the house and furnishings. Using commercial filters containing activated-carbon downstream of the installed ESP, reduced the indoor steady state ozone concentrations between 6 % and 39 %.
Citation: Environmental Science and Technology
Pub Type: Journals
electrostatic precipitator, ultrafine particles, ozone, filtration, sustainable buildings