This paper describes the approach used during the upgrading of an alkoxylation facility which resulted in the removal of the reactor bursting discs thus avoiding the need to install dump tanks. Inherently safe operating conditions, now ensured by a high integrity process control system, were determined by extensive calorimetric studies to measure the heats of reaction and degree of accumulation during the process. The experimental methods used to characterize both the highly exothermic process reaction as well as the runaway reactions are described. Both types of reaction show non-ideal temperature-pressure behaviour and, in the case of ethylene oxide, are also highly toxic. The evaluation of the results obtained and justification for the decisions taken are elaborated in the paper.