# Risk Assessment of Hydrogen Cyanide for Available Safe Egress Time in Fire Simulation
## 3 Simulation Results and Discussion of Fire Scenarios
### Fire Growth Rate Sensitivity Analysis Results  
The simulation results using the fire growth curve of the residential building presented in Figure 2 were analyzed through Figures 4 and 5. Although the 'Medium' FGR applied in the fire growth curve is based on statistical data from PBD assessment reports, it does not represent all fire scenarios. Since simulation results for specific fire scenarios can yield limited insights, it is necessary to consider a broader range of fire scenarios. Therefore, this study examined the impact of varying fire growth rates to determine how the fire risk related to HCN can increase by varying the FGR across seven conditions from 'Slow' to 'Ultra-fast'.  
Figure 6 compares the times at which each parameter reaches the threshold values specified in the life safety code under varying FGR conditions. In this analysis, only the parameters with the highest RRS identified in Figure 5 (visibility, gas temperature, and HCN concentration) are shown. From the results of GM21 in Figure 6a, under the 'Slow' FGR condition, visibility reaches the threshold value at 178 s, while HCN concentration reaches the threshold at 481 s, indicating a difference of 303 s. As FGR increases, the time for each parameter to reach the threshold value decreases in an inverse proportionality manner, with a difference of approximately 33 s under the 'Ultra-fast' condition. From the results in Figure 6b, the gas temperature reaches the threshold value first, with gas temperature reaching it at 292 s and HCN concentration at 374 s under the 'Slow' FGR condition. In summary, the difference in the time for gas temperature and HCN concentration to reach the threshold value is 82 s under the 'Slow' condition and 17 s under the 'Ultra-fast' condition. Overall, as FGR increases, the time for each parameter to reach the threshold value decreases inversely, indicating a potential increase in the risk posed by HCN concentration.  
Figure 5: Relative risk score evaluation of parameters using time to reach threshold value.  
Figure 7 shows the RRS evaluation results for the times at which each parameter identified in Figure 6 reaches the threshold values of the life safety code under varying FGR conditions. For GM21, as FGR increases, the RRS of all parameters except CO concentration exceeds approximately 80 points. Specifically, under the 'Ultra-fast' FGR condition, the RRS for visibility, gas temperature, and HCN concentration are evaluated to be 100, 99, and 91.8 points, respectively. Notably, as FGR increases from 'Slow' to 'Ultra-fast', the RRS for HCN concentration increases from 28.2 points to 91.8 points, showing scores similar to those of visibility and gas temperature. Similarly, for PAN, the RRS for HCN concentration also shows a high score of up to 79.5 points. Consequently, as FGR increases, the RRS for all parameters generally increases, and HCN concentration, in particular, shows results comparable to the risk scores for visibility and gas temperature.  
Figure 6: Comparison of time to reach threshold values of parameters with fire growth rate.  
Figure 7: Relative risk score evaluation of parameters with fire growth rate.