Design and Preliminary PM2.5 Characterization of a Low-Cost Zeolite–Titanium Dioxide Air Filtration Device

Abstract

This study presents the design and preliminary fine particulate matter (PM2.5) characterization of a low-cost air-filtration device intended to reduce localized exposure to air pollution in densely populated and high-traffic communities. The fan-driven device combines two minimum efficiency reporting value (MERV) 13 filters, a clinoptilolite zeolite bed, and an exterior anatase titanium dioxide (TiO2) coating for particulate filtration and potential gas-phase adsorption and photocatalysis. Quantitative analysis focused on PM2.5 because the AirGradient Open Air monitor reported nitrogen oxides (NOx) only as a relative index. Testing used a repeated-measures alternating OFF/ON crossover design at a residential site in Essex County, New Jersey, across four sessions using controlled particulate loading; two sessions met a prespecified concentration gate for pooled analysis. Paired OFF-ON differences were evaluated using a two-sided Wilcoxon signed-rank test with a prespecified significance level of 0.05. Across 29 pooled block pairs, mean PM2.5 was 1.10 µg m^-3 (9.6%) lower during ON than OFF blocks; 17 of 29 paired differences were positive (W = 135.5, p = 0.076), and the result did not reach the prespecified significance threshold. Larger-scale testing with paired sensors is needed to determine whether the observed difference is reproducible and to evaluate quantitative NOx performance.