The assessment of likelihood of the thermal explosion occurrence caused by runaway Maillard chemical reaction in sugar crystallisation process is presented. Logical model of that unwanted event was established and afterwards the formal risk assessment was undertaken. Hazard identification determined the parameters responsible for initiation, development and final occurrence of runaway The Maillard reaction and the fault tree analysis was performed to present the logical model. The quantitative risk analysis was carried out using event tree method. The probability of thermal explosion evaluated seems to be non-accepted and hence the additional risk control measures in the form of three-stage safety system were proposed. The basic principles for the construction of such st system were suggested.