WISE colour–colour plot for the sources of the sample, separated into H i detections (filled symbols) and H i non-detections (empty symbols). Dust-poor galaxies are green squares, 12μm bright sources are orange pentagons and 4.6μm bright sources are black triangles. Interacting sources are grey diamonds. The dashed lines indicate the cut-offs of the WISE colours we used to classify our sources. Further details on the classification of the sources are shown in Table 1.