Shield assembly for a gas sensor

A shield assembly for protecting a sensing element of a gas sensor, the shield assembly includes an outer shield comprising an elongated outer wall and an inner shield comprising an inner elongated wall. The elongated outer wall includes a first end, a second end, and a tip portion disposed across the second end of the outer wall. The tip portion includes at least one elongated aperture extending therethrough and the elongated outer wall is configured to not have any openings between the first end and the second end. The inner elongated wall is disposed within the elongated outer wall. The inner elongated wall includes a first open end, a second open end, and a flange portion extending from a periphery of the first open end of the inner elongated wall. The flange portion is configured to make contact with the elongated outer wall when the inner elongated wall is inserted therein and the second open end makes contact with the tip portion to define a thermal barrier comprising a cavity located between the inner elongated wall and the elongated outer wall, wherein convection losses from an interior region defined by the inner elongated wall, to the elongated outer wall, are slowed by heated fluid disposed in the cavity between the elongated outer wall and the inner elongated wall.