A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis (EPMA), was applied to characterize samples collected at a subway station and ambient samples in Seoul. According to their chemical composition, many distinctive particle types were identified. For samples collected at the subway station platform, the major chemical species are carbon-rich, organic, aluminosilicates (AlSi), AlSi/C, AlSi/$CaCO_{3},;CaCO_{3},;SiO_{2},;and;Fe_{2}O_{3}$. For outdoor samples, carbon-rich, organic, AlSi, $CaCO_{3},;SiO_{2},;NaNO_{3},;(Na,Mg)NO_{3},;Na(CO_{3},NO_{3},SO_{4}),;and;(NH_{4})_2SO_4$, are abundantly encountered. Samples collected at the subway station show very high contents of $Fe_{2}O_{3}$, both in coarse and fine fractions, which come from brake block, subway train wheel, electric contact materials, etc. It is demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in indoor and outdoor samples.