Pressure-sensitive tape is often used to bind explosive devices. It can become important trace evidence in many cases. Three types of calcium carbonate (heavy, light, and active CaCO3), which were widely used as additives in pressure-sensitive tape substrate, were analyzed with Fourier transform infrared spectroscopy (FTIR) in this study. A Spectrum GX 2000 system with a diamond anvil cell and a deuterated triglycine sulfate detector was employed for IR observation. Background was subtracted for every measurement, and triplicate tests were performed. Differences in positions of main peaks and the corresponding functional groups were investigated. Heavy CaCO3 could be identified from the two absorptions near 873 and 855/cm, while light CaCO3 only has one peak near 873/cm because of the low content of aragonite. Active CaCO3 could be identified from the absorptions in the 2800-2900/cm region because of the existence of organic compounds. Tiny but indicative changes in the 878-853/cm region were found in the spectra of CaCO3 with different content of aragonite and calcite. CaCO3 in pressure-sensitive tape, which cannot be differentiated by scanning electron microscope/energy dispersive X-ray spectrometer and thermal analysis, can be easily identified using FTIR. The findings were successfully applied to three specific explosive cases and would be helpful in finding the possible source of explosive devices in future cases. Abstract published by arrangement with John Wiley & Sons.