# Building Fire Evacuation: An IoT-Aided Perspective in the 5G Era
## 1 Introduction  
Rapid urbanization and increases in the urban population have resulted in high-density development and erection of tall buildings in cities. Large complex tall buildings can accommodate over ten thousand occupants. Their safety should be a great concern of building designers, engineers, and governments. In June 2017, the world was all astounded by the Grenfell Tower fire in London, UK. The fire caused the entire building to burn out, causing 80 deaths and over 70 injuries [1]. Delayed building evacuation was considered to be one of the factors leading to the great loss of life in that fire [2]. In the Grenfell Tower fire, a \"stay-put\" policy was initially employed [3]. The \"stay-put\" policy suggests that residents not directly affected by the fire should remain within their flats and wait for further notice [2]. This policy was made because a fire in such a building would usually be contained within the floor of origin, and it is expected that occupants other than those living or staying near the fire origin may not need to evacuate. However, the Grenfell Tower fire spread dramatically and was soon out of control, making the \"stay-put\" policy totally lose its functions. The abandonment of the \"stay-put\" policy was made very late, when the thick toxic smoke had already spread to the single narrow stairwell in the building. As the only escape route was blocked, only a few residents successfully escaped after relinquishing the \"stay-put\" policy. There were indeed many people trapped in their rooms on high-level floors. To lead to such a situation, the following possible points may be considered:  
1. Information concerning the fire-ground may be insufficient, e.g., fire development situation, first-aided and subsequent firefighting resource allocation, evacuation process, and so on. In the Grenfell Tower fire, due to a lack of feedback on fire-ground information about fire development, trapped occupants, and evacuation progress, the incident commander (IC) may not have had sufficient information to judge if the evacuation tactics should be altered, so that the occupants may not have been alerted to escape immediately. Like the Grenfell Tower fire, currently, collections of fire-ground information of most of the other building fires can only depend on the reports by firefighters who have entered the building. This sort of information collection mechanism may delay and make it hard for ICs to obtain the full picture of the fire development situation immediately and affect the IC's decision-making process. 2. Lack of effective communication means to alert building occupants. The Grenfell Tower may not have been equipped with the public address (PA) system or other effective means of communication to advise the occupants of the fire situation and escape arrangement [4]. The only two ways that the IC could alert the occupants inside the building were through the physical deployment of firefighters to each floor or to notify the occupants directly from the control room using phone calls. Both approaches were time-consuming and difficult to operate. Although conditions in the stairs did not present an insurmountable hurdle at first, full evacuation of the building was not considered timely. The same situation can be suffered by any type of buildings around the world. Due to the lack of effective means of communication to alert and assist building occupants in these buildings, evacuation of the occupants can be seriously delayed. 3. Difficulty of organizing an effective evacuation. Even if all the occupants in the building were successfully notified to evacuate, a sudden evacuation would cause a mass gathering of people in stairwells and reduce the evacuation efficiency. For tall building evacuation, it is necessary to control the sequence and means of evacuation for each building floor in order to make the evacuation remain orderly and more efficient. However, it is not easy to carry out such an organized evacuation strategy.