Compartmentation prevents fire from spreading through cavities and penetrations within the structure of your building.
When electrical and mechanical services are installed, holes are made through partition walls for penetrants such as pipework, wiring and risers. Any open holes (voids) between rooms will allow smoke and heat to transfer quickly from one room to the next.
Building regulations require that any vertical or horizontal voids between areas should be treated with an intumescent sealing material to limit the spread of fire, the same is true for movement joints within the building.