[en] Regarding CO₂/O₂-based mixture as an arc quenching gas in high-voltage circuit breakers, the predominant component species present in high numbers at temperatures of 300–20 000 K are determined in consideration of addition of CF₃CFCH₂ (hereinafter written as C₃H₂F₄) gas to the CO₂/O₂-based mixture. In the determination, not only are 87 gaseous species but also condensed-phase carbon (hereinafter written as C(c)) taken into account as component species. The evaluation results reveal that CO₂, O₂, CF₄ and HF in gaseous phase behave as the predominant component species at 300–1000 K for lower content additive-gas, whereas the species C(c) is also generated as the predominant component at the same temperature for higher content additive-gas.

Subsequently, reactions of chemical elements C, O, F and H to form the above-described chemical species are successfully expressed using CO₂, O₂ and C₃H₂F₄ contents as stoichiometric coefficients. Expressing the reactions furthermore enables us to formulate the prevent condition of the C(c) generation as a function of O₂ content and C₃H₂F₄ content . Similar formulations are successfully performed for CO₂/O₂/C4-FN and CO₂/O₂/C5-FK mixtures. (paper)