There are increasing developments and uses of building materials which have sorptive and reduction ability for chemicals in indoor air, and test method for reduction performance of them has been required. For formaldehyde reduction performance test of those materials, JIS A 1905 was established Feb. 2007. Our group has developed the air flow control unit for 20L small chamber in order to evaluate reduction performance of sorptive building materials. JIS A 1905 describes the two methods [part. 1

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... : Measurement of adsorption flux with supplying constant concentration of formaldehyde hereinafter, Constant Concentration Supplying Method CCSM)) and part. 2 : Measurement of capability for suppressing formaldehyde emission hereinafter, Emission Material Method EMM))] for reduction performance test, but differences of test methods might provide different result values even if the same material was tested. In this paper, when changed area ratios i.e. loading factor) of specimens under the same test method, it was investigated what differences would be made in performance values. As a result, when changed area ratios of specimens, sorption flux showed different values depending on area ratios but equivalent ventilation rate was less affected by area ratios. However, under the same area ratio condition, sorption fluxes showed even and steady values, while equivalent ventilation rates did fluctuating values depending on changes of chamber concentrations. When the same sorptive material tested, sorption fluxes gained from CCSM JIS A 1905-1) showed 1.6 for sorptive material DM) and 3.2 for sorptive material TG) times higher values in compared with EMM JIS A 1905-2). It was suggested that compensation of formaldehyde concentration with HBF equation could improve the performance value from EMM and reduce the disagreement between CCSM and EMM. JIS A 1905 2007 JIS A 1906 2008 JIS A 1905 JIS A 1905 2.2m 2 /m 3 2.2m 2 /m 3 2/3 76 659 35-41 2011