Caesium hydrogen sulfate, CsHSO4 is a solid acid proton conductor, which operates in the temperature range from 100 to 200 °C. Hence, it has potential application in intermediate temperature fuel cells as a solid electrolyte. CsHSO4 shows a complex phase diagram, with three ambient pressure phases known. Phase I is reversibly obtained above 141 °C and shows a high proton conductivity, the superprotonic phase. A recent MAPS proposal was able to observe the O¿H stretch of CsHSO4 in phases III, II and I for the first time. This showed a clear shift that indicates a change in the O-H and OH....O distances. This proposal seeks to use SANDALS to provide complementary structural information on these crucial distances that are not available in the literature.