## 4 Results and Discussion
### Weight Analysis of Risk Assessment System  
To verify the accuracy and superiority of the CWM, the weights obtained by ORM, EWM, and CWM for the same second-level index are presented in Figure 7. It can be observed that the weights of ORM tended to be related to the importance order--the more important the index, the bigger its weight. In poisonous gas management, the importance ratio for both indices are 1, which means that they are equally important; therefore, there is no difference in importance of these first-level indices, which could explain why the ORM weights in Figure 7d do not completely match the importance order. Furthermore, the weights obtained by EWM can be seen to under-estimate the risk of the first index and over-estimate the last index, which may lead to the ignorance of the first index's risk or exaggeration of the last index's risk. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**First-Level Indices**} & \multirow{2}{*}{**Number**} & \multicolumn{5}{c}{**Weights of Secondary-Level Indices**} \\ \cline{3-6}  & & \(w_{1}\) & \(w_{2}\) & \(w_{3}\) & \(w_{4}\) \\ \hline Blast furnace safety performance & \(W_{1}\) & 0.2996 & 0.2078 & 0.2958 & 0.1967 \\ Protective facility & \(W_{2}\) & 0.3801 & 0.1910 & 0.2183 & 0.2106 \\ Evacuation and dilution facilities & \(W_{3}\) & 0.2533 & 0.2533 & 0.2536 & 0.2398 \\ Poisonous gas management & \(W_{4}\) & 0.3477 & 0.2496 & 0.4027 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Weight vectors of first-level indices. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multirow{2}{*}{**First-Level Indices**} & \multirow{2}{*}{**Number**} & \multicolumn{5}{c}{**Evaluation Set**} \\ \cline{3-8}  & & **Excellent** & **Good** & **Moderate** & **Defective** & **Poor** & **Max \(\{f_{i}\}\)** & **Result** \\  & & \(f_{1}\) & \(f_{2}\) & \(f_{3}\) & \(f_{4}\) & \(f_{5}\) & & \\ \hline Blast furnace safety performance & \(F_{1}\) & 0.8581 & 0.0715 & 0.0704 & 0 & 0 & \(f_{1}\) & excellent \\ Protective facility & \(F_{2}\) & 0.8971 & 0.0628 & 0.0402 & 0 & 0 & \(f_{1}\) & excellent \\ Evacuation and dilution facilities & \(F_{3}\) & 0.7733 & 0.1253 & 0.1014 & 0 & 0 & \(f_{1}\) & excellent \\ Poisonous gas management & \(F_{4}\) & 0.8652 & 0.0945 & 0.0403 & 0 & 0 & \(f_{1}\) & excellent \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The value of evaluation sets of toxic gas leakages. The weights calculated by CWM avoided the lack of accuracy that might occur with ORM or EWM weights. For example, the weight of \(u_{21}\) in the protective facility category obtained by CWM was bigger than ORM and EWM. Actually, \(u_{21}\) is the most important index in the protective facility category, and the membership value \(r_{21}\) is 1, which indicates that all of the experts confirmed that the safety level of \(u_{21}\) was excellent. Therefore, the CWM result precisely reflected the actual situation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**First-Level Indices \(V_{i}\)**} & \multirow{2}{*}{**Evaluation Set**} & \multirow{2}{*}{**SCM Evaluation Result**} & \multicolumn{4}{c}{**Membership \(r_{ij}\)**} \\ \cline{5-6}  & & & \(r_{ij}\) & \(r_{2j}\) & \(r_{3j}\) & \(r_{4j}\) \\ \hline \multirow{3}{*}{\(V_{1}\)} & excellent & 0.85 & 0.8 & 0.7 & 1 & 0.9 \\  & good & 0.075 & 0.1 & 0.2 & 0 & 0 \\  & moderate & 0.075 & 0.1 & 0.1 & 0 & 0 \\ \hline \multirow{3}{*}{\(V_{2}\)} & excellent & 0.875 & 1 & 0.8 & 0.8 & 0.9 \\  & good & 0.075 & 0 & 1 & 0.2 & 0 \\  & moderate & 0.05 & 0 & 0.1 & 0 & 0.1 \\ \hline \multirow{3}{*}{\(V_{3}\)} & excellent & 0.775 & 0.7 & 0.7 & 0.8 & 0.9 \\  & good & 0.075 & 0.1 & 0.2 & 0.1 & 0.1 \\  & moderate & 0.1 & 0.2 & 0.1 & 0.1 & 0 \\ \hline \multirow{3}{*}{\(V_{4}\)} & excellent & 0.833 & 1 & 0.8 & 0.8 & 0.9 \\  & good & 0.1 & 0.2 & 0.1 & 0 & - \\ \cline{1-1}  & moderate & 0.033 & 0 & 0 & 0.1 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Evaluation value of the safety checklist method.