Effects of Photocatalysts on the Efficiency and Pressure Drop of HEPA Filters in Removing Airborne Microorganisms: A Scoping Review

Recent years have seen many attempts to increase the efficiency and reduce the pressure drop of High-Efficiency Particulate Air Filter (HEPA) filters in removing microorganisms through shape change and the use of photocatalysts. This study is the first scoping review of the effects of photocatalysts on increasing the efficiency of HEPA filters in the elimination of airborne microorganisms.

PubMed, Scopus, Irandoc, and Magiran databases were searched for relevant articles. Based on select keywords and the study objectives and applying the inclusion and exclusion criteria, eight from a total of 315 articles were identified, two of which were typical in the review of efficiency and pressure drop. These articles investigated the effect of photocatalyst and filter shape on the efficiency and pressure drop of HEPA filters.

These studies were released from 2000 to 2021. TiO2, with its long-term interactions with microorganisms, the attack of superoxide radicals (O2•−), and the release of K+, RNA, proteins, and other essential components will cause their destruction. Ultraviolet rays at a wavelength of 254 nm remove bacteria on the surface of the filter. The synergy of the inherent ability of UV radiation with TiO2 through nucleic acid and protein damage in microorganisms and the generation of oxidative radicals increases the efficiency of HEPA filters compared to either one alone.

The photocatalysts with ultra-violet rays on the HEPA filter can reduce the problem of microorganism growth and increase indoor air quality.