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The electric or hybrid vehicles need fast switching operation in order to ensure the quick-response of the motors. This process is carried out by compact direct-current contactors which are designed to perform the switching over multiple cycles. During the contact separation, the gas between the contacts breaks down and the resulting thermal arc provides a conductive channel that sustains the current. Until the arc is quenched, the current continues to flow through the contacts despite the physical separation. This unintended flow of current could lead to a larger response time than the safe operation limits. We perform high-fidelity simulation of thermal arc in hydrogen-nitrogen mixture environment under external magnetic field of 1 Tesla. The hydrogen enrichment level is kept at 0%, 40%, 50% and 80%. The contacts are separated at 8 m/s. It is demonstrated that the increase in hydrogen concentration leads to smaller arc lifetime thereby improving the circuit interruption performance.