Comparison of S X (or S⁹⁺) effective collision strengths between the present work (M20), Liang et al. (2011, L11), Wang et al. (2018, W18) and Bell & Ramsbottom (2000, R-matrix) as incorporated in the CHIANTI atomic database v9.0.1 (C-901) for selected transitions listed in Table 4. The top panel is a dipole transition from the ground level, followed by two metastable transitions. The bottom two panels are forbidden transitions from the ground level to the first two metastable levels.