Fluorescent lamp that is coated with a photocatalyst film, titanium dioxide (TiO2), can catalyze the microorganisms and smell producing molecules that touch the membrane. In this report, we examined the effect of this coated lamp by the number of floating microorganisms or smell molecules in a room installed with this lamp. The number of floating microorganisms was examined independently in different laboratories before and after installing the lamps in an animal facility and a vegetable processing room of a food company. We found that the number of floating microorganisms was significantly reduced after the installation of this coated lamp. To test for smell molecules, acetaldehyde was injected into a closed chamber installed with the coated lamp and the result was compared to a control where a regular fluorescent lamp was used. The acetaldehyde concentration did not change with the regular lamp but was halved after 1h with the photocatalyst coated lamp. To test the effect in real settings, questionnaires were filled out by restroom users in several different places. About 90% of those surveyed answered that there was a reduction of smell after the installation of the photocatalyst coated lamp. We concluded that the installation of this coated fluorescent lamp reduced not only the floating microorganisms but the smell in various practical situations.