The need for UV irradiation requires the circulation of air through a specific point, which makes it impossible to protect oneself from contaminated air. The production rate of (OH●) radicals is low and obtained at low concentrations, so the entire biochemical reaction time is long, ranging from 15 to 360 minutes.
The technologies mentioned above are only effective in small spaces. A large number of chemical reactants such as H2O2, TiO2 or Fe2+ are required in the production process of (OH●), resulting in high costs and safety issues due to the generation of toxic degradation intermediates and deactivation of the material in order to increase the production of (OH●), requiring several types of technologies and, as a result, large equipment.