What is photocatalytic oxidation?

• A. A method of filtering incoming air without UV.
• B. A way of filtering recirculated air using UV rays with a TiO2-coated filter.
• C. An approach to purify drinking water.
• D. A technique for reducing building energy use.

Answer: (B)

Photocatalytic oxidation is a process where UV light activates a catalyst, typically titanium dioxide, coated on a surface. When air passes over this illuminated surface in an HVAC system, reactive species form and oxidize pollutants like VOCs and microbes, breaking them down rather than just trapping them. In practice, this means a filter is coated with TiO2 and irradiated with UV light so recirculated air continually encounters the activated catalyst, leading to chemical oxidation of contaminants on contact. This differs from simply filtering incoming air without UV, and it isn’t primarily about drinking water purification or reducing energy use, which is why using UV-activated TiO2 on a recirculated-air filter best describes photocatalytic oxidation.