Herschel SPIRE 250 μm map of M 33 (Xilouris et al. 2012). Units are Jy/(18′′ beam). Circles mark the position and beam size of the ISO/LWS [C ii] observations along the major axis of M 33. The ellipse delineates the galacto-centric distance of 4.5 kpc, which devides the observed inner (N1 and S1) and outer (N2 and S2) regions. The white square marks the BCLMP 302 H ii region. Coordinates are RA and Dec. (Eq. J2000).