Designing pressure relief devices for three-phase systems consisting of solids, liquids and vapors requires an in-depth knowledge of the fluid dynamics and of the thermodynamic effects in the reactor. The behavior of foaming three-phase systems is, to date, still not well understood. In this research, these systems are systematically studied, taking the solid properties into account. Also, the applicability of two-phase pressure relief models to three-phase systems is investigated with the help of the simulation tool SAFIRE/Vent. The results obtained contribute significantly to the better design of pressure relief devices and to more accurate predictions of the three-phase venting behavior and the solid discharge.