A methodology for estimating indoor sources contributing to PM.

Quantifying source contributions to indoor PM levels by indoor PM sources has been limited by the costs associated with chemical speciation analyses of indoor PM samples. Here, we propose a new methodology to estimate this contribution. We applied FUzzy SpatioTemporal Apportionment (FUSTA) to a database of indoor and outdoor PM concentrations in school classrooms plus surface meteorological data to determine the main spatiotemporal patterns (STPs) of PM.