“Early Studies Characterizing Household Dirt”

2001:60: Millette

Microscope, 49(4): 201-208


Early work by the Hoover Company characterized household dirt by a number of parameters including particle size and particle type. Hoover researchers used microscopy, sieving, and other tests to characterize dirt collected from 56 cities in studies starting in 1928. The average particle size distribution data suggested that 65% of the particles were larger than 300 um, 30% were between 75 um and 300 um, and approximately 5% were smaller than 75 um. Microscopical and chemical analysis showed that the combustible constituents included: cellulosic fibers (cotton, paper, wood), animal fibers (hair, wool), gums, resins, fats, oils and rubber particles. The noncombustible (inorganic) material included soil minerals (quartz, feldspar), and particles of soil or building materials (gypsum, limestone, dolomite). Reports in 1961 (University of Nebraska) and 1975 (Hoover’s North Canton Study) found similar particle size distributions.

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