The sick house syndrome is occurred from the harmful elements that the building interior materials are given off after building construction or renovation. The appropriate methods, which is to prevent sick house syndrome from spreading have to be selected before building construction or renovation. Thus, this study is to measure the density of formaldehyde, one of the volatile organic compounds after sprinkling air-assisted-catalyst on the building interior space. As a result, the emit value of formaldehyde is measured 0.07ppm that is lower than the standard of Environmental Protection Agency and World Health Organization, 0.1ppm, and the standard of Ministry of Health, Labour, and Welfare of Japan, 0.08ppm.