Abundance ratio of the S-bearing species in each region of NGC 253 (red shaded area), and in various Galactic environments. For NGC 253, the listed sequence of clouds follows the layout of the GMCs of the CMZ as shown in Figs. 1–3. The ratios are between species for which the emission size is similar, and is constrained (top panel) or unconstrained/extended (≥1.6″; bottom panel). The underscore numbers 1 and 2 refer to the low- and high-E_u component, respectively. For the outflows and shocks (blue shaded area), we compare with the prototypical shock L1157-B1 (Holdship et al. 2019, and references therein) and the Orion KL Plateau (Persson et al. 2007; Tercero et al. 2010; Esplugues et al. 2013; Crockett et al. 2014a,b; Gong et al. 2015). The hot cores (HCs; yellow shaded area) are Orion KL (Feng et al. 2015; Luo et al. 2019), Sgr B2 (N) (Neill et al. 2014), and Cyg X-N12 (El Akel et al. 2022). The PDRs (green shaded region) are the Orion Bar (Jansen et al. 1995; Leurini et al. 2006) and Mon R2 (Ginard et al. 2012), two high-UV irradiated PDRs. Finally, the molecular clouds category (purple shaded area) comprises dark clouds on the one hand (L1544, L483, and B1-b; Fuente et al. 2016; Vastel et al. 2018; Lattanzi et al. 2020), and Galactic Centre (GC) Clouds on the other hand (Nummelin et al. 2000; Martín et al. 2005 and references therein, Armijos-Abendaño et al. 2015). Lower and upper limits are marked with filled triangles. The legend on the bottom part of the plot is associated with NGC 253. For Galactic environments, the same colour code applies.