Complex and tall buildings have been constructed in many cities recently. Fire safety should be a major concern of building designers, engineers, and governments. Previous fire experience has made us understand the importance of acquiring fire-ground information to facilitate firefighting operations, evacuation processes, rescues, etc. Recently, the rapid advancement in Information Technology, Data Analytics, and other detection and monitoring systems has provided the basis for fire safety researchers to re-think fire safety strategies in the built environment. Amongst all fire safety studies, evacuation in tall buildings, including elevator evacuations, has attracted much attention. IoT-aided building fire evacuation is a new concept of the building evacuation mode, which improves the building evacuation process by making decisions of escape based on the real-time fire-ground information, such as the fire environment and occupant situations. Focusing on IoT applications in building fire evacuation, this paper explores the advantages and insufficiencies of current smart building fire evacuation systems. A conceptual design of an IoT-aided building fire evacuation control system is described. The system is introduced in the sequence of information needs, information sources and data transmission, and potential services and applications. Finally, new insights into promising 5G technologies for future building fire evacuations are discussed.