Abstract: A smoke detection unit has a detection chamber for sampling smoke from a surrounding environment. The detection chamber allows air circulation but is optically opaque. This configuration is typical of photoelectric smoke detectors, for example. A housing defines a window though which air from the environment circulates into and out of the detection chamber. The window's height is approximately the same as the chamber. A cage vane is positioned in the window and is configured as an inverted frustoconical member. An inner edge of the cage vane is spaced away from the chamber. The angled vane, along the other aspects of the unit's configuration, improves sensitivity by increasing smoke circulation through the chamber. This configuration guides the air currents typically created by fires at the ceiling so that the smoke flows easily into the detection chamber.