Abstract: A viewer for improving the visibility of Halide gas leak detectors, and comprising an observation tunnel embracing the flame shield of the detector at one closed end, open at the other end for closure by the face of the person making the observation directly by eye, and characterized by inlet and exhaust ventilators at opposite ends thereof and the later operating as a chimney for convection flow of heated flame gases, the ventilators being of labyrinth form obscuring outside light from the tunnel.