A retention assembly secures a hydrocarbon trap within an air intake path of an internal combustion engine. The hydrocarbon trap is positioned within a first air tube, such as an outlet duct of a clean air filter. A second air tube, such as an inlet portion of a clean air duct assembly, is fitted over a portion of the first air tube to enclose the hydrocarbon trap within the first air tube. A clamp is fitted over both the first and second air tubes. A plurality of radially-extending, circumferentially-spaced protrusions that are formed on an inner surface of the second air tube pass through a respective plurality of apertures formed in the first air tube and, under radial compression exerted by the clamp, engage an outer surface of the hydrocarbon trap, thereby securing the trap within the first air tube.