Laboratory comparison of relative performance of gas phase filtration media at high and low O₃/NO₂ challenge concentrations (ASHRAE RP-1557)

Abstract

To guide the selection and design of air filter/cleaning devices for improving indoor air quality (IAQ), it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for low concentration conditions (∼50 ppb) under which they are applied. Our study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE Standard 145.1 (ASHRAE 2008) would also perform well at low concentrations, typically indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration properties, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (∼1 ppm/100 ppm) and low (∼50 ppb) levels of O₃/NO₂ concentration for all media selected. Existing models were evaluated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that (1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results and (2) no existing models were suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.