Recently, Monn et al. (1997) and Luoma and Batterman (2001) showed that in indoor environments, e.g., in homes and offices, where there is no specific source of pollution (like smoking and the combustion of fuel for heating and/or cooking), occupant-related activities may represent a principal source of dust (composed of cloth fibers, hair fragments, soil particles, skin cells, resuspended particles of various origin by walking, and emissions from materials handled, such as paper, fungi spores, and fibers, etc.).