Abstract: C₅F₁₀O mixed gas is a potential substitute for SF₆ in medium- and low-voltage gas insulated equipment. However, its long-term compatibility with the commonly used sealing materials inside the equipment has not been revealed yet, which hinders its application in the power industry. In this paper, a 28-day thermal accelerated aging experiment was carried out to simulate the long-term interaction between C₅F₁₀O and two commonly used rubber EPDM and NBR. The stability of C₅F₁₀O and the sealing properties of EPDM and NBR were then analyzed with X-ray photoelectron spectroscopy and gas chromatography. According to the results, under long-term coexistence conditions, C₅F₁₀O can react with the sealing rubbers and generate decomposition products such as CO, CO₂, C₃F₆ and C₃F₇H. After the thermal accelerated aging, the compressive modulus of EPDM and NBR declined to 90.6% and 88.4% of the initial state, respectively. After the reaction with C₅F₁₀O, the F elements that were not original contained in EPDM and NBR appeared on the rubbers' surface and mainly existed in the form of C—F and Zn—F bond. Hence, the interactions are not only related to the main copolymer, but also to the reinforcing agents such as ZnO. The results indicate that EPDM and NBR have poor compatibility with C₅F₁₀O, and it is essential to take protective measures or specify the replacement cycle for sealing materials in the operation and maintenance of related equipment.