Top: non-LTE calculations with RADEX of the (5−4) to (2−1) line ratios for the typical conditions for n(H₂) and N(SiO) in massive clumps. Solid lines show the estimated line ratios for T_kin = 50 K, and 250 K in varying shades corresponding to different line area ratios, which are comparable to the observed values. Dashed lines show the estimated line temperatures for the (2–1) transition with a beam filling factor of unity. Bottom: the same calculations as above for the T_kin = 50 K compared with the observed line temperatures for the (2–1) transition and the line ratio, where both values are normalised to a line width of 5 km s^-1. Solid lines show the solutions for the given values of H₂ density; dashed lines show the solutions for fixed SiO column density.