Removal of formaldehyde from indoor air by passive type air-cleaning materials

We have developed a board-like air-cleaning material consisting of activated carbon particles and manganese oxides, by which HCHO gas is decomposed into carbon dioxide even at room temperature. In this study, we investigated removal efficiencies of the air-cleaning board in a passive mode using a kinetic approach. First-order removal rate constant, k, corresponding to air change rate was characterized for the board as a function of the ratio of applied board area to space volume, S/V, and was found directly proportional to S/V with a slope of 25 at 25°C. The performance of the board was evaluated in a full-size laboratory with a constant gas generation. The board suppressed the increase of indoor HCHO concentration and the time course fitted to a theoretical curve. Then, field tests of the air-cleaning board were conducted in newly constructed multi-family houses in Japan from May 1998 to January 1999. The board not only reduced indoor HCHO concentration from 0.21 to 0.04 ppm for more than 7 months, but also enhanced the loss of HCHO gas from building materials in apartments.