A technique for determining the temperature of optically nongray particles is considered. Novel approximate relationships are proposed for the spectral emissivity of dusty media. The spectral approximations of a single-scattering albedo are derived for the particles of combustion products. The polydispersions of CeO2 and ash particles in the flow of propane-air flame combustion products have been measured. The particle temperature. refractive index and mean diameter are obtained.