The purpose of the study is to develop sampling strategies and bioassay methods for indoor air in homes, the authors developed a medium-volume sampler to collect the <10 - micrometers particulate matter and semivolatile organics, and used high-volume particulate sampler for comparison. The percent organic extractable and polycyclic aromatic hydrocarbon (PAH) content of the filter and XAD-2, as well as the distribution of the organic matter, were determined. The mutagenicity of the filter and XAD-2 samples was determined by the Ames Salmonella mutagenesis assay. Most PAH compounds collected in the XAD-2 resin were equal to or smaller than 4-ring compounds and had lower mutagenic activity than the filter sample. Compounds contained in the filter samples included 3- to 7-ring PAHs, and showed higher mutagenic activity than XAD-2 samples. The coal combustion emitted both direct- and indirect-acting mutagens, most of which were frameshift mutagens. (Copyright (c) 1987 the American Chemical Society.)