Synthetic non-LTE LVG spectrum of the Class 0 protostar Serpens MM1 convolved to PACS (top three panels) and SPIRE (lower panel) spectral resolutions. Continuous curves show the line emission contribution from the “hot” (red), “warm” (green) and “cool” (blue) components discussed in the text. Vertical labels mark the wavelength position of CO (red), H₂O (blue), OH (cyan), ¹³CO (magenta), HCO⁺ and HCN (grey) rotational transitions. [O i]63, 145 and [C i]370, 609 μm fine structure lines are marked with green labels.