A system that may include a mechanical stage that is arranged to move an object along a predetermined path in relation to an optical module during an illumination of the object by the optical module; a structural support element that is arranged to support at least a part of the optical module; a gas flow module that is arranged to direct clean gas towards the object through gas flow module openings that define a coverage area that is (a) bigger than the object and (b) is positioned directly above at least a majority of the object when the object is positioned anywhere along the predetermined path.