Four widely used organic peroxides, namely DTBP, DTAP, BTDH and TBPB, were investigated for hazards caused by their thermal instabilities. Chemically pure materials without diluents were adopted to reveal their thermal decomposition and associated kinetic processes. DSC was employed to carry out experimental thermal study and the Friedman isoconversional method, the Kissinger method, as well as AKTS software were used for kinetic calculations and numerical simulations. Experimental results showed TBPB had the lowest detected "onset temperature", and unlike DTBP, DTAP and BTDH, all of which showed a two-stage decomposition, TBPB decomposition occurred in a single stage. Heats of reactions measured by ARC were between ca. 37 and 54% of the heats of reaction measured by DSC and reported elsewhere by both, DSC and ARC. The obtained values are compared and discussed. Then, a risk diagram was established to determine the conditionally acceptable conditions of use for the OPs. Furthermore, pressure evaluation results by TSu indicated the generation of non-condensable gas during runaway reactions should be seriously considered. (C) 2014 Elsevier B.V. All rights reserved.