Risks of multiphase processes are based on the interaction between mass transfer, kinetics of chemical reactions, phase equilibrium and multiphase heat transfer. It is not sufficient to consider only kinetic terms in safety analysis of these processes. Besides events taking place in the reactor, all important devices in the reactor periphery (heat exchangers, pumps etc.) and all major functions of process control including the installed protective systems also have to be taken into account. Procedures and systems for early-warning and for avoidance and mastering critical events can be defined and tested. The ethoxylation of fatty alcohols in a gas-liquid semibatch reactor is dicussed as an example for the procedure of safety analysis by dynamic simulation of failures.