# A BIM-Based Smart System for Fire Evacuation
## 2 Materials and Methods
### Smart Evacuation System Framework  
The smart evacuation system is composed of five layers (Figure 1): (1) a physical layer; (2) a monitoring layer; (3) a smart platform layer; (4) a control and alert layer; and (5) a smart services layer. The following sections present each of the layers of this system. 1. Physical Layer  
Fire propagation and people evacuation are affected by the building's geometry and space distribution [6]. Consequently, the fire evacuation system should include data concerning the spatial organization of the building, materials used in the construction, building equipment, and the fire components. The building's geometry information is required for indoor navigation by considering the obstacles (walls, columns, furniture) and doors. The building materials' characteristics, including their thermal properties, are necessary for simulating fire scenarios, understanding spaces' function, and equipment location to help recognize the fire source and severity. Moreover, data related to the firefighting equipment such as fire detectors, extinguishers, alarms, and emergency evacuation should be integrated into the model for optimal evacuation management. Finally, data concerning the physical layer are integrated into the BIM model and shared with users, the management team, and emergency services. 2. Monitoring Layer  
Smart sensors are used for building supervision and fire evacuation management. Detectors are used to monitor flames, heat, smoke, and other combustion products. The most commonly used sensors to deal with fire hazards are temperature, smoke, and Carbon Dioxide (CO\({}_{2}\)). Sensors collect and transmit data to the system in real time. They are placed in critical locations to collect and share data with the smart platform. The real-time location of humans in the building constitutes a vital issue in evacuation management. A wide variety of Radio Frequency (RF) sensors are used for real-time location systems (RTLS). However, most of these sensors do not provide accurate results and coverage. Therefore, Ultra-Wide Band (UWB) is used for comprehensive fire risk management [36; 37]. Figure 1: Architecture of the smart evacuation system. Data transfer is accomplished via wired or wireless technologies. Wireless networks transmit collected data to the server, where data are processed and analyzed. Routers are installed inside the buildings to ensure good communication coverage. Each router operates as a checkpoint to take over the other router task and transfer it to the next one. Users effectively participate in fire evacuation management by using mobile applications to share real-time information about the fire event. 3. Smart Platform This layer comprises both data processing and analysis. * Data Processing: Data processing includes data cleaning and storage. Data cleaning aims to detect inaccurate records to replace, modify, or even delete the coarse data. This step is important since incorrect or irrelevant data can lead to a wrong action. For this reason, data collected from sensors and stakeholders should be cleaned to avoid bad decisions. Data storage concerns the integration of collected data in one database. Furthermore, the platform offers the ability to access the storage to search for a particular event. To realize this task, the platform must be accompanied by a XQuery that links the database with the Web world. XQuery allows access to the database by granting the possibility to store, extract, and manipulate data. * Data Analysis: Data analysis aims to transform the collected data into operational data, which improves fire evacuation operations. The BIM environment offers the capacity to set up norms, including minor and upper limits for sensors; whenever these boundaries are reached, BIM could identify the fire source and type. These norms concern temperature, CO2, and smoke. * Evacuation Simulation: FDS generates several fire scenarios based on different fire locations, types, and severity.