Thermal pressure versus incident radiation field in several PDRs. Red points are from Young Owl et al. (2002) (based on FIR line analysis), green points are from Joblin et al. (2018) (based on high-J CO line analysis), dark blue points are from this study (M42 S is the southern Veil Shell, M42 SE is the southeastern Veil Shell, M42 E1 and M42 E2 lie in the bright eastern arm of the Veil Shell (cf. green circles 1 and 2 in Fig. 15)). The green dashed line is the fit by Wu et al. (2018) (based on high-J CO line analysis). The dashed gray line is the analytic solution of Seo et al. (2019), once divided by 3 to account for pressure equipartition.