## 3 Results
### Environmental Effects of PMVE/N\({}_{2}\) Gas Mixture  
Compared with SF\({}_{6}\), PMVE exhibits a very low global warming potential (GWP) and N\({}_{2}\) has a GWP value of zero. The mixing of PMVE with N\({}_{2}\) further reduces the overall GWP of the gas mixture. Additionally, PMVE has a short atmospheric lifetime, thereby minimizing its potential for atmospheric damage. The atmospheric degradation of PMVE does not lead to the generation of long-chain acids that are of environmental concern [32]. At the same time, the safety of using a PMVE/N\({}_{2}\) gas mixture must be carefully considered. The inhalation of C\({}_{2}\)F\({}_{4}\) (tetrafluoroethylene, CAS: 116-14-3) has an LC50 (4 h, rat inhalation) of 164,000 mg/m\({}^{3}\), indicating low toxicity. Similarly, the inhalation of C\({}_{3}\)F\({}_{6}\) (hexafluoropropylene, CAS: 116-15-4) has an LC50 (4 h, rat inhalation) of 11,200 mg/m\({}^{3}\)  
\begin{table}
\begin{tabular}{c c c} \hline
**No** & **Reaction** & **Reaction** **Enthalpy (kcal/mol), T = 298.15 K** \\ \hline A1 & C\({}_{3}\)F\({}_{6}\)O \(\rightarrow\) CF\({}_{3}\)OC\({}_{2}\)F\({}_{2}\) + F & 116.67 \\ A2 & CF\({}_{3}\)OC\({}_{2}\)F\({}_{2}\) \(\rightarrow\) CF\({}_{3}\)O + C\({}_{2}\)F\({}_{2}\) & 59.34 \\ A3 & CF\({}_{3}\)O \(\rightarrow\) CF\({}_{2}\)O + F & 22.37 \\ B1 & C\({}_{3}\)F\({}_{6}\)O \(\rightarrow\) C\({}_{2}\)F\({}_{3}\) + CF\({}_{3}\)O & 103.70 \\ B2 & C\({}_{2}\)F\({}_{3}\) \(\rightarrow\) C\({}_{2}\)F\({}_{2}\) + F & 72.30 \\ B3 & C\({}_{2}\)F\({}_{3}\) + F \(\rightarrow\) C\({}_{2}\)F\({}_{4}\) & \(-\)121.12 \\ C1 & C\({}_{3}\)F\({}_{6}\)O \(\rightarrow\) C\({}_{2}\)F\({}_{3}\)O + CF\({}_{3}\) & 47.12 \\ C2 & CF\({}_{3}\) + F \(\rightarrow\) CF\({}_{4}\) & \(-\)121.81 \\ D & C\({}_{2}\)F\({}_{3}\) + CF\({}_{3}\)\(\rightarrow\) C\({}_{3}\)F\({}_{6}\) & \(-\)103.15 \\ E & 2 CF\({}_{3}\)\(\rightarrow\) C\({}_{2}\)F\({}_{6}\) & \(-\)89.02 \\ F & C + O \(\rightarrow\) CO & \(-\)354.76 \\ G & 2 CN \(\rightarrow\) C\({}_{2}\)N\({}_{2}\) & \(-\)142.87 \\ \hline \end{tabular}
\end{table}
Table 2: Proposed decomposition mechanism and reaction enthalpies of PMVE/N\({}_{2}\).  
Figure 7: Free radical recombination of PMVE/N\({}_{2}\) decomposition process. (Light blue for F atom, red for O atom, gray for C atom and dark blue for N atom).  
categorizing it as a low-toxicity substance. However, the inhalation of CF2O (carbonyl fluoride, CAS: 353-50-4) is much more hazardous, with an LC50 (4 h, rat inhalation) of 270 mg/m\({}^{3}\), clearly classifying it as highly toxic. CF2O has a strong irritant effect on the respiratory mucosa and can lead to chemical pneumonia and pulmonary edema. Additionally, the decomposition of PMVE/N2 also produces CO (carbon monoxide, CAS: 630-08-0) and C2N2 (cyanogen, CAS: 460-19-5), which pose significant health risks. The inhalation of CO has an LC50 (4 h, rat inhalation) of 2069 mg/m\({}^{3}\). CO binds with hemoglobin in the blood, leading to cardiovascular toxicity and potential harm to the respiratory system. The inhalation of C2N2, with an LC50 (1 h, rat inhalation) of 350 ppm, is also highly toxic, causing respiratory paralysis and irritation. Furthermore, C2N2 is flammable and poses additional safety concerns. Therefore, before the PMVE/N2 gas mixture is implemented, it is crucial to evaluate the toxicological properties of the decomposition products to ensure the safety of both equipment and personnel.