A circuit breaker with metallic enclosure comprising a chamber, the chamber enclosing an interior volume (311, 312) and the chamber comprising a first compartment and a second compartment, wherein the first and second compartments enclose the interior volume and wherein the first and second compartments are electrically insulated from each other, a switching actuator displaceably provided inside at least one of the compartments (31, 32) and configured and adapted to selectively provide electric connection between the compartments, and a sealed tank enclosing the chamber and electrically insulated from the chamber, whereby an exterior volume is provided between a wall of the tank and the chamber, wherein each of the compartments is connected to a line connector (312, 322) penetrating the tank, wherein the penetration opening of each line connector through the tank is sealed and the line connectors are electrically insulated from the tank, wherein the tank and the compartments contain a dielectric gas and the interior volume (311, 321) of each compartment of the chamber is fluidly connected to the exterior volume by a flow path having an overall flow cross section, characterized in that the flow path between the interior volume of each of the compartments and the exterior volume is subdivided into a multitude of ducts, each duct having a partial flow cross section, a hydraulic diameter and a length, wherein the length of each duct is at least twice the hydraulic diameter of the duct, wherein at least one duct extends from an inlet adjacent the interior volume (311, 321) of a compartment (31, 32) to an outlet adjacent the exterior volume, and wherein further a lateral fluid connection between the duct and the exterior volume is provided and joins the duct between the inlet and the outlet such that colder gas from the exterior volume is entrained through the lateral fluid connection by hot gas flowing through the duct from the interior volume to the exterior volume, the colder gas thereby being mixed with the hot gas. a switching actuator displaceably provided inside at least one of the compartments (31, 32) and configured and adapted to selectively provide electric connection between the compartments, and a sealed tank enclosing the chamber and electrically insulated from the chamber, whereby an exterior volume is provided between a wall of the tank and the chamber, wherein each of the compartments is connected to a line connector (312, 322) penetrating the tank, wherein the penetration opening of each line connector through the tank is sealed and the line connectors are electrically insulated from the tank, wherein the tank and the compartments contain a dielectric gas and the interior volume (311, 321) of each compartment of the chamber is fluidly connected to the exterior volume by a flow path having an overall flow cross section, characterized in that the flow path between the interior volume of each of the compartments and the exterior volume is subdivided into a multitude of ducts, each duct having a partial flow cross section, a hydraulic diameter and a length, wherein the length of each duct is at least twice the hydraulic diameter of the duct, wherein at least one duct extends from an inlet adjacent the interior volume (311, 321) of a compartment (31, 32) to an outlet adjacent the exterior volume, and wherein further a lateral fluid connection between the duct and the exterior volume is provided and joins the duct between the inlet and the outlet such that colder gas from the exterior volume is entrained through the lateral fluid connection by hot gas flowing through the duct from the interior volume to the exterior volume, the colder gas thereby being mixed with the hot gas.