Fig. 3. Noncontact repellent assay system set-up with volunteer subject sitting in the testing position.forearms fixed in position. There is a metal support frame around the screen barrier that provides a gap of 1 cm (0.4 in.) between the forearm and the screen barrier to prevent mosquitoes from making direct contact with the skin surface as configured in study I (Fig. 2). In study II the metal support frame and screen was removed from one chamber side, allowing the mosquito direct contact with the treated skin surface.