The DSC (Differential Scanning Calorimetry) analysis of heavy ozonized C60 fullerene (known also as “fullerene ozopolymer”), shows the exothermal decomposition of this compound with a peak at 158°C with a decomposition enthalpy ΔHdec ≈ −322 kJ/mol and an activation energy for the decomposition E# = 71 kJ/mol. These experimental facts confirm the secondary ozonide/peroxidic and polymeric nature of fullerene ozopolymer originally suggested by the infrared spectroscopy analysis and solid state 13C-NMR spectroscopy. It is also shown that the secondary ozonide group of fullerene ozopolymer can be reduced selectively by a treatment with hydrogen iodide.