Ozone interactions with HVAC filters
Experiments were conducted in a laboratory to investigate ozone interactions with HVAC filters. Experimental results indicate that activated carbon filters can effectively remove ozone, used commercial HVAC filters remove more ozone than used residential HVAC filters, and for most filters the ozone removal efficiency declined rapidly and converged to a non-zero steady-state value. Experimental results also indicate that repeated exposure of residential and commercial filters to ozone following a 24-hour period of no exposure led to a regeneration of ozone removal efficiency. Experimental results suggest that filter material, manufacturer, particle loading, operation time and operation location affect ozone removal on HVAC filters. A plug flow reactor model was developed to investigate the ozone removal process and a time scale analysis was used to analyze the fundamental processes involved with ozone reactions on filters. The steady-state ozone removal efficiency on HVAC filters is speculated to be limited by either ozone or reactant diffusion inside particles, and regeneration is due to internal diffusion of reactive species to sites available to ozone for reaction. Experiments were also conducted in a laboratory to evaluate ozone removal on small filters loaded with either diesel or oleic acid particles. Filters loaded with oleic acid vi had one to two orders of magnitude less particle surface area but greater ozone removal capacity than filters loaded with diesel particles. Ozone removal capacity was observed to be proportional to the mass of oleic acid particles on filters. The results presented in this study should facilitate future studies related to ozone chemistry in HVAC systems, and may ultimately lead to the design of filters that effectively reduce the exposure of building occupants to ozone.