The benzene desorption behavior of microporous, sputtered amorphous hydrogenated carbon (a-C:H) films has been investigated using thermal desorption spectroscopy (TDS). This forms the basis of a temperature limitation mechanism for solar evacuated tubular collectors (ETCs) which depends on the reversible adsorption/desorption of benzene by the spectrally selective, graded a-C:H/stainless steel cermet film in the collector vacuum space. Desorption spectra show two coverage-dependent peaks. An Arrhenius-Redhead mechanism is not appropriate to describe the spectre. A simple model for desorption from a microporous film has been developed and fitted to experimental data. The model combines desorption and evaporation processes with film characteristics obtained using other methods.