Gas Phase Air Cleaner Technologies: Abilities and Limitations

Air cleaning technologies like activated carbon (AC) filters and photocatalytic oxidation (PCO) process are commonly used in commercial air purifiers, with some anecdotal evidence supporting their effectiveness. These technologies, when functioning efficiently, can enhance indoor air quality (IAQ), reduce chemical contaminants, and lower energy use by minimizing the need for high outdoor air exchange rates by mechanical ventilation systems. However, TiO2-based PCO filters often show low to moderate activity in degrading common volatile organic compounds (VOCs), such as alkanes, alcohols, ketones, aromatics, and aldehydes, under HVAC-like conditions. Furthermore, limited studies have investigated PCO performance when treating complex VOC mixtures, where interactions between compounds can alter degradation pathways and by-product formation. A significant challenge in PCO systems is catalyst deactivation over time, which leads to a decline in performance, yet this issue remains underexplored. In contrast, AC filters have long been used for VOC removal, and their effectiveness depends on factors such as AC properties, surface functional groups, and the properties of VOCs, as well as operational parameters. This paper presents a review of these two technologies. The abilities and limitations of each technology are discussed. The impact of each influencing factor on the quality of air and energy consumption will be presented.