[OI]_63μm (red line) and CO (16–15) (grey line) spectra, and {T_mb [OI_63μm]}/{T_mb [CO (16–15)]} ratio (green points) obtained at nominal spatial resolutions, channel by channel, in NGC1333-IRAS4A RI (upper panel, from Kristensen et al. 2017), Cep E-BII (middle panel), the central position of the G5.89–0.39 massive star-forming region (from Leurini et al. 2015). The line ratio is only shown for channels where both lines have been detected above the 3σ threshold. Horizontal black lines at 0.5, 1, 1.5, and 2 values are shown in relation with this ratio as a guide for the eye in both panels.