An integrated approach has been developed for the multi-component analysis of indoor PM2.5 collected onto the same quartz fiber filter (QFF) by using an innovative combination of techniques such as inductively coupled sec-tor field plasma mass spectrometry (ICP-SF-MS) with vapor-phase microwave-assisted aqua regia or sonication-assisted water extraction, ion chromatography, thermal–optical transmittance as well as high performance liquid chromatography and enzyme-linked 5,5′-dithio-bis(2-nitrobenzoic acid) assay for the determination of elemen-tal composition, major inorganic ions, elemental/organic carbon (EC/OC) as well as oxidative potential (OP) through ascorbate (AA) and reduced glutathione (GSH) depletion, respectively. The low mass of PM 2.5 collectable indoors, the elemental blank values of the QFFs and the sample volume/acidity requirements of the ICP-SF-MS represented a challenge for elemental determination. Finally, this approach was successfully applied for determi-nation of 15 elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn and Pb) at the ng m −3 level in more than two-thirds of indoor PM 2.5 (n = 25) collected in mechanically ventilated offices within the European Union pro-ject OFFICAIR at increased sampling flow rates (0.6 m 3 h −1 –2.3 m 3 h −1) and sampling time (cca. 100 h) in the acidic/aqueous extracts. The concentration of Cl − , NO 3 − , SO 4 2− , Na + , NH 4 + , K + , Ca 2+ , Mg 2+ , OC and EC was at the μg m −3 level in the aqueous extracts. This new approach aiming at the comprehensive characterization of low mass indoor PM 2.5 samples allowed assessment of OP AA and OP GSH in all samples. The PM2.5 critical sample mass to achieve elemental determination was approximately 400 μg.