Abstract: A circuit breaker is provided having a particle trap within an interior gas-insulation cavity containing a contact mechanism. The interior cavity is defined within a tank. In an embodiment, the tank has a generally cylindrical tank wall, and the trap is a recessed channel formed by the tank wall along a bottom of the interior cavity. The trap is effective to collect foreign particles present within the tank, thereby reducing breakdown. In an embodiment, portions of the tank wall adjacent to the channel curve or slope downwardly toward the channel to guide particles moving under the influence of gravity, mechanical vibration and gas flow into the trap where they are immobilized in operation due to the low electrical field.