For industrial semi-batch emulsion polymerization, it is difficult to predict the composition of the reactor contents during a runaway reaction since many recipes are involved and it actually may be a fault in the feeds to the reactor that leads to the runaway reaction, as a distributed control system cannot safely prevent wrong feeds. Therefore, in order to safeguard the reactor, very high kinetics need to be taken into account, as discussed theoretically as well as based on an example. Corresponding maximum temperature increase rates may be above 100 K · min−1. This needs to be taken into account when designing safety measures for emulsion polymerization reactions. As a result, large safety relief valves or rupture discs may need to be installed.