## 2 Conditions and Methods for Fire Simulation  
### Fire Simulation Conditions  
Prediction results for smoke and heat dispersion were obtained using FDS (version 6.7.9) and CFAST (version 7.7.0) to evaluate the performance of different fire models. We compared the smoke concentration and temperature predictions of CFAST with those of FDS for the computational domain of a corridor shape with a high aspect ratio, as shown in Figure 1. Figure 1a is the calculation domain considered in FDS, which is set to 3.6 m (x) \(\times\) 2.4 (y) \(\times\) 2.4 (z) based on the ISO 9705 compartment size, and a corridor geometry extending 12 m in the longitudinal direction (x) is considered. To directly compare the prediction results of FDS and CFAST, openings in the compartments were not considered. Smoke and heat detectors were installed at 2.4 m intervals, following the ISO 9705 standard size, to predict the smoke concentration and temperature. Figure 1b illustrates the computational domain of CFAST, where the \"compartments\" feature of CFAST was employed. An area covering a distance equal to the width of the compartment (W) was set in accordance with ISO 9705. Four conditions were considered, including a corridor shape divided at intervals equivalent to the width (1W, 2W, and 5W). This nomenclature was assigned to these conditions. Furthermore, under all the conditions, a 1.0 m square fire source was located at the center of ISO 9705. Various fire conditions were applied to the fire simulation inputs to evaluate the predicted activation times of the smoke and heat detectors, as shown in Figure 2. Importantly, the generation of smoke and the temperature rise during the initial fire stage can vary significantly according to the fire growth rate. Four conditions--slow, medium, fast, and ultrafast--from NFPA 92 B [17] were considered, with the same maximum heat release rate (HRRmax) of 1.0 MW. Each fire scenario was configured to reach the HRR of 1.0 MW and maintain it for 1000 s before termination. With these different fire growth curves set as boundary conditions, the appropriate initial stage of the fire was considered, and the activation times of the smoke and heat detectors were evaluated. Additionally, the smoke concentrations, temperatures, and flow rates at fire detector locations were predicted to estimate their activation times. The fuel selected for the fire growth curve implementation was n-heptane (C\({}_{7}\)H\({}_{16}\)). Details regarding the properties of the additional fuel [18,19] and input parameters for the fire detector prediction methods are presented in Table 1. These input parameters for heat and smoke detectors were set according to a database of experimentally measured results from previous studies. The selection of the grid size is important for ensuring the reliability of the prediction results of FDS, which can then be compared with the prediction results of CFAST [20]. In fire simulations, the grid size can be determined according to the characteristic fire  
Figure 1: Schematic and scale of the computational domain for heat and smoke diffusion. diameters in Equation (1) [21]. Generally, good prediction results can be achieved when 4-16 grids [22] or 10-20 grids [23] are set up inside \(D^{*}\). \[D^{*}=\left(\frac{\dot{Q}}{\rho_{\infty}c_{p}T_{\infty}\sqrt{g}}\right)^{\frac{ 2}{8}} \tag{1}\]  
Here, under standard conditions (20 \({}^{\circ}\)C, 1 atm), \(\rho_{\infty}\) represents the air density (kg/m\({}^{3}\)), \(c_{p}\) represents the specific heat (kJ/kg\(\cdot\)K), \(T_{\infty}\) represents the absolute temperature (K), \(g\) represents the gravitational acceleration (m/s\({}^{2}\)), and \(\dot{Q}\) represents the maximum HRR of the fire source used in this study. With the maximum HRR applied in this study as the reference, i.e., \(D^{*}=0.05\) m, the selected grid size is deemed sufficient, considering a method that uses the characteristic fire diameter, which includes 16 grid cells.