Designation for a grille made of wood or metal, usually attached to one half of the cellar door. It allows the fermentation gases(carbon dioxide) to escape during fermentation despite the closed wine cellar or press house. However, if the fermentation room is lower than the cellar entrance, this can still be dangerous. Such devices used to be widespread, especially in cellar alleys in the Weinviertel (Lower Austria). The fermentation gas was also discharged via the so-called steam pipe. However, both devices are only suitable to a limited extent because the toxic carbon dioxide is heavier than air and therefore collects at the bottom or at the lowest point. Today, the carbon dioxide is extracted via exhausters (deaerators) and led outside or in large cellars, also in containers, and recycled. See also under candle tasting and wine-growing customs.