Phases at which photoionisation occurs for different ISM species as a function of radius. The lines correspond to the peak ionisation rate, and the shaded region indicates the phases between which 80% of photoionisation occurs. The fading corresponds to the limit where < 5% of the gas is ionised in total. The ± 1 mag range of the ionising flux is not considered in this plot. The phases of the spectra taken of SN 2013gh (dotted lines) and iPTF 13dge (dashed lines) indicate which radii are probed for photoionisation.