The modified Stoessel criticality diagram was present in this research. The final temperature under adiabatic condition was considered for thermal hazard assessment. We reported the systematic thermal hazard assessment of synthesis of tert-butyl peracetate, preparation of hydroxylamine and synthesis of 2,6-diethyl-4-methylPhenylpropanamide and discussed their classification according to the modified Stoessel criticality diagram. The process temperature, maximum temperature of synthesis reaction, maximum temperature for technical reasons, temperature at which TMRad is 24 h and the final temperature under adiabatic condition(T-p, MTSR, MTT, T-D24, T-f) were obtained by experiments and calculation. The evaluation results by the modified Stoessel criticality are more rational and conforms to reality. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.