The facility above the borehole, and the storage cavern, pumps hydrogen into and out of the cavern. It has pipes and fittings like valves that open and shut the pipes similar to a bathroom tap.Compressors inject the hydrogen into the storage facility (comparable to an air pump increasing the pressure in a ball), increasing the pressure in the cavern.When the hydrogen comes out of the cavern, it goes through a hydrogen drying plant. Since water was used in the construction of the cavern, the hydrogen, which in itself is dry, may contain residual moisture. This moisture must be removed before the hydrogen can be used in the fuel tanks of trucks, buses and other vehicles.The quality of the hydrogen (for example how pure it is and how much moisture it contains) is measured carefully prior to injection into the cavern storage facility and after its offtake from the cavern.