Various features from the excitation and radiative transfer models for a low mass loss rate object (ST Cam) and a high mass loss rate object (CRL 190). Top panels: radial abundance profiles of CS, SiO, and SiS. Middle panels: calculated velocity-integrated intensities for the observed lines of CS, SiO, and SiS as functions of the impact parameter. Bottom panels: calculated ratio of excitation temperature to kinetic temperature (T_ex ∕T_k) as a function of radius for observed lines of CS, SiO, and SiS. Solid lines correspond to the model in which IR pumping is included,whereas dashed lines correspond to the model excluding IR pumping. The SiS abundance in ST Cam corresponds to an upper limit.