Housing device

The unit has a main body (1) with connected passage socket (3) to create an air passage into an interior chamber. The body wall defines a fitting opening, and part of the socket is fitting part (2). Peripheral sections of opening and fitting part have complementary joint structures (6) for connection. A wall section (3b) of the socket is formed by the main body. The main body has a holder groove, and the fitting part has a corresponding tongue. The unit forms part or all of an air filter box. It consists of thermoplastic synthetic material.