The purpose of this research is to know the present status of the indoor air chemical pollution by VOCs in Japanese houses in 2000. The concentrations of formaldehyde, toluene, xylene and ethylbenzene were measured in five thousand houses, and the following results were obtained. 1) In 27.3% of surveyed houses, the indoor concentrations of formaldehyde exceeded the guideline established by the Ministry of health, labor and welfare of Japanese Government. And those of toluene, xylene and ethylbenzene were 12.3, 0.013 and 0% respectively. 2) The formaldehyde concentrations correlated well to the indoor temperatures. 3) The averages of the formaldehyde concentrations in houses according to the age of year after construction were analyzed, and the concentration in houses built after 1997 was lower than that in 1996, which showed the highest value.
