Individual OH spectra and 8 μm images. For each maser site, the top panels show the spectrum/spectra identified in this region, and the bottom panels present the corresponding GLIMPSE 8 μm image (Benjamin et al. 2003; Churchwell et al. 2009). Where GLIMPSE data are not available, the corresponding WISE data (Wright et al. 2010) are used. The grey-shaded parts in the spectra outline the velocity regimes of the individual maser spots, and the circles, squares, diamonds, and plus-signs mark the positions of the 1612, 1665, 1667, and 1720 MHz maser spots, respectively (spatially overlapping ones are sometimes difficult to visually separate).