Prediction of the ditetrazole test set using this impact sensitivity model in conjunction with the trigger hypothesis failed to produce good predictions (Figure , green triangles). We propose two explanations for this outcome. Firstly, many of the ditetrazoles used in the external test set are fully conjugated. Our model for tetrazole impact sensitivity largely featured descriptors that describe the π-system of isolated tetrazole motifs. Consequently, the extended conjugation of the non-symmetric ditetrazole test set might produce cooperative effects that our model fails to explain. An alternative explanation is that the trigger hypothesis is simply not applicable for impact-initiated decomposition of tetrazoles. The investigation of this question is an area of ongoing research.