Name for various devices made of glass, which are placed on the sealing hole of the fermentation container and seal it tightly on one side. Other names are fermentation bell, fermentation control attachment, fermentation tube, fermentation tube, fermentation bung and fermentation closure. This is the access of oxygen and unwanted oxidation prevented. That is why one is carried out fermentation also known as "closed fermentation". The attachment is half filled with water and functions as a valve. Water is also common sulfur dioxide added. The escaping during fermentation carbon dioxide is passed through and this is indicated optically or additionally acoustically. There are various forms or even very simple devices in which one on the bung attached hose is led into a container filled with water.