Abstract: A ventilator or extractor unit is disclosed for mounting at an aperture in a wall, duct, window pane or the like. The unit includes a first approximately annular part which in use is secured to the window pane or the like with a central aperture in said annular part in register with the aperture in the window pane or the like. A further generally annular part is spaced from the first-mentioned annular part on the side of the first-mentioned part remote from the window pane or the like, the further annular part being supported from the first-mentioned part by four pillars at the peripheries of the annular parts. A second part in the form of a circular lens, is supported centrally, approximately midway between the annular parts.