An active carbon filter for an air vent assembly comprising: a cylindrical housing that in use is located coaxially within an air supply duct, the housing having a height, a diameter, an inlet end and an outlet end, the housing comprising an outer part having a frusto conical shape and comprising a perforated outer wall and a perforated inner wall spaced from the outer wall such that a void is defined between the inner and outer walls, the inner wall having a complementary shape corresponding to the shape of the outer wall such it nests within the outer wall in a spaced relationship, and the inner part of the housing having a frusto conical shape and comprising an inner wall and an outer wall, the inner part being arranged radially inwards of the outer part such that it extends within the outer part from the inlet end of the outer part towards the outlet end of the outer part; and an active carbon material contained within the void of the outer part; wherein the diameter of at least the outer wall of the frusto conical outer part of the housing tapers in the direction of the inlet end from a first diameter at the outlet end to a smaller diameter at the inlet end such that the outer wall is increasingly spaced from the duct along its height in the direction of the inlet end when located within the duct to allow air flowing through the duct from the inlet end to flow into the perforations of the outer wall, across the active carbon material and out of the perforations in the inner wall, and the inner part tapers radially inwards in the opposing direction to the outer part towards the outlet end of the outer part. a cylindrical housing that in use is located coaxially within an air supply duct, the housing having a height, a diameter, an inlet end and an outlet end, the housing comprising an outer part having a frusto conical shape and comprising a perforated outer wall and a perforated inner wall spaced from the outer wall such that a void is defined between the inner and outer walls, the inner wall having a complementary shape corresponding to the shape of the outer wall such it nests within the outer wall in a spaced relationship, and the inner part of the housing having a frusto conical shape and comprising an inner wall and an outer wall, the inner part being arranged radially inwards of the outer part such that it extends within the outer part from the inlet end of the outer part towards the outlet end of the outer part; and an active carbon material contained within the void of the outer part; wherein the diameter of at least the outer wall of the frusto conical outer part of the housing tapers in the direction of the inlet end from a first diameter at the outlet end to a smaller diameter at the inlet end such that the outer wall is increasingly spaced from the duct along its height in the direction of the inlet end when located within the duct to allow air flowing through the duct from the inlet end to flow into the perforations of the outer wall, across the active carbon material and out of the perforations in the inner wall, and the inner part tapers radially inwards in the opposing direction to the outer part towards the outlet end of the outer part.