Results of the benchmark tests. Top panels: SEDs of dust spheres that are heated externally by a diluted black body for various extinctions (as labelled). The SEDs are normalised to the total energy. Results are shown for HII (black solid) and MC (magenta dashed). Bottom panels: residuals are given as absolute relative errors (%) of MC compared to HII. We see that the results derived by both methods agree well with each other.