Nuclear microprobe was used to measure single aerosol particles (SAPs) indoors from Shanghai. Every particle is characterized
with its micro-PIXE spectrum, which can be considered as the fingerprint of the SAPs. The pattern recognition technique (PR)
was applied to trace the SAPs back to their source. Results of five monitor homes at different locations in Shanghai show
that most of the measured indoor aerosol particles are derived from soil dust, cement dust, vehicle exhaust, coal boilers
and steel mill dust.