The DRI Model 2015 Multiwavelength Thermal/Optical Carbon Analyzer enhances the widely used for quantifying organic carbon (OC), elemental carbon (EC, also termed Black Carbon [BC]), and temperature-separated carbon fractions on aerosol filter deposits. Thermal/optical carbon analysis is based on the preferential oxidation of OC and EC materials under different temperatures and atmospheres. A ~0.5 cm2 punch from a particle-laden quartzfiber filter (or other sample form) is heated in programmed temperature steps. Organic compounds are liberated under a non-oxidizing helium atmosphere at lower temperatures up to 580 °C, while EC is combusted in an oxidizing atmosphere with 2% O2 at temperatures up to 840 °C. The liberated carbon is oxidized to carbon dioxide (CO2) by heated manganese dioxide (MnO2), and the CO2 is quantified by an NDIR detector. Seven modulated diode lasers measure the reflectance from, and transmittance through, each filter at wavelengths from 405 to 980 nm.