## 4 Results and Discussion
### Evaluation Result Analysis of First-Level Indices  
For the blast furnace safety performance index, the evaluation vector \(F_{1}\) was (0.8581, 0.0715, 0.0704, 0, 0). According to the principle of the maximum membership [35], the evaluation result of this index is \"excellent\". At the same time, according to the evaluation sets, the value of \"excellent\" was much higher than other evaluation sets, and there was not much difference between the values of \"good\" and \"moderate\". Thus, we can come to the conclusion that the blast furnace safety performance was stable and safe, under the current circumstances. For the protective facility index, the evaluation vector \(F_{2}\) was (0.8971, 0.0628, 0.0402, 0, 0). The evaluation result of this index is \"excellent,\" with a value of 0.8971, which is the highest in this evaluation set. The sum of the values of \"good\" and \"moderate\" occupied nearly 0.1, such that the protective facilities in the plant could be considered to satisfy the overall safety demands regarding toxic gas leaks; however, there was still room for growth. For the evacuation and dilution facilities index, the evaluation vector \(F_{3}\) was (0.7733, 0.1253, 0.1014, 0, 0). The evaluation result of this index was \"excellent\". At the same time, the value of \"excellent\" was less than 0.8, which means that the safety status of evacuation and dilution facilities was not optimal. As a result, it can be concluded that the overall evaluation result was \"excellent\", but vulnerable factors in the evacuation and dilution facilities needed to be checked. For the poisonous gas management index, the evaluation vector \(F_{4}\) was (0.8652, 0.0945, 0.0403, 0, 0). The evaluation result of this index is \"excellent\". Consequently, the management of poisonous gas was proper, and the risk of toxic gas leaks caused by lack of management was relatively low. The overall evaluation result of the toxic gas leak risk in this steel plant was \"excellent\", corresponding to the actual risk level of the steel plant. The results illustrate that the overall risk level of gas leaks in the considered steel plant was well under control. The factors of gas leak risk remained stable and safe, and the probability of gas leakage accidents occurring was relatively low. Meanwhile, we can see from Table 5 that the safety level of evacuation and dilution facilities was relatively low compared to the other indices, and the safety levels associated with the corrosion degree of the gas tank and CO monitoring alarm devices were relatively high. Therefore, attention should be focused on the fragile factors in the chain, according to the RAS results. In steel plants, one of the most basic safety management methods is the safety checklist method (SCM), which is commonly adopted in industrial safety management. The steel plant in this study adopted risk classification and control, with the classification of the risk based on a safety management method. The calculation result for the safety checklist method for each first-level indicator is given as the average value of \(r_{1}\) of its secondary indices, as shown in Table 6.  
In order to validate the RAS evaluation result, the RAS and SCM evaluation results were compared, as shown in Figure 8. According to Figure 8, there was little difference between the evaluation results. The excellent values of \(V_{2}\) and \(V_{4}\) obtained through the RAS were slightly bigger than those of SCM. The reason for this is that the importance and numerical authenticity of each index are not considered in the evaluation process for SCM; additionally, the actual situations of \(V_{2}\) and \(V_{4}\) in the steel plant are well-managed, and the risk of a gas leak is relatively low.