An exhaust gas purifying member comprises a housing an exhaust gas purification block placed in the housing, and an exhaust gas purification block-retaining element inserted in an annular space between the housing and the block. The retaining element is, during manufacture of the member, made from a material including at least one nonfunctional component intended to disappear after a characteristic period of using the member. A method of manufacturing the member comprises assembling the housing, the retaining element, and the exhaust gas purification block to obtain a housing whereof a diameter is equal to a predetermined diameter, and with the installation density of the retaining element being equal to a target installation density after the characteristic usage period of the member.