Indoor air quality has received tremendous attention these days because people generally spend more than 80 % of their time in indoors. This indicates that people are placed in more risky situation form inhalation of pollutants due to the level of pollutants in indoor environment is higher than in outdoor environment. The ventilation is known as the most convenient and effective solution to hedge the risk but it’s not in metropolis such as Seoul because the ventilation could migrate particulate matters from vehicular exhaust or industries. Therefore, air cleaning by air purifier is considered as the most feasible option to improve indoor air quality so air purifier market size has been skyrocketing.

At the current stage, photocatalytic decomposition has shown to be a promising and effective technology for pollution control. Unlike traditional method such as adsorption by activated carbon which merely relocates pollutants from indoor environment to deodorizing filter, photocatalysts actually disintegrate pollutants to CO₂ and H₂O. However, photocatalysts are still immature to replace activated carbon because the decomposition rate of pollutants by photocatalysts is quite slower than the adsorption rate of activated carbon. In addition, photocatalytic efficiency is decreased with decreasing pollutant concentration which represents indoor environment. Therefore, we believed that adsorbents and photocatalysts must be combinated to maximize the efficiency of indoor air quality improvement by air purifier...