DECLINE OF VOC CONCENTRATIONS WITH AGING OF HOUSES IN JAPAN

The purpose of this investigation is to know the long term characteristics of VOC concentrations inhouses built before the building code in 2003 and to know the need of the countermeasures in thehouses were already built for example the improvement of the living habit, ventilation and buildingmaterials. The concentrations of VOCs were measured in these houses from 2000 to 2005. The resultsshowed that the concentration of formaldehyde decreased in the first year. After that the decline of theconcentration became invisible and the concentration changed only with the temperature. Thecharacteristic of decline was thought to be caused by the two mechanisms of emission. One is anemission of concealed formaldehyde in the process of material production and another is an emissionwith the generation of formaldehyde from adhesives of urea resin and moisture. The concentration oftoluene decreased rapidly in the first year. The concentrations of xylene, ethyl-benzene and styreneshowed a similar change. But the concentrations of acetaldehyde which were measured from thesummer of 2002 did not decrease and its concentrations in some houses were higher than theguideline even in the winter of 2005.