Combat frogmen (Kampfschwimmer) operate offshore undiscovered and in shallow water, but mine clearance divers are used also in lakes and partly into deeper water. The preferred diving equipment of the combat frogmen is accordingly oxygen rebreathers, which reprocesses breathed out air and delivers only small masses of gas to the environment, so that the combat frogman cannot be discovered by rising bubbles. See also German commando frogmen. Clearance divers use either compressed air or mixed gas devices. With "oxygen cycle devices" the depth is limited to ; with "compressed air diving devices", which are used also in sport diving, the depth is ; with "mixed gas devices" with trimixes the oxygen portion according to the depth is reduced, thus the possible depth is higher. Since 2002 their compressed air diving devices "FTG" were replaced by computer-controlled mixture rebreathers called "Stealth". Apart from the mechanical and electronic special tools used by mine clearance divers, items of equipment are used which are also used by civilian divers. The mine clearance diver boat "Mūhlhausen" (replacement for the "Stier" which was decommissioned in 1994) and the diver school boat "Langeoog" (replacement for the "ansa") in Eckernförde have stationary decompression chambers for up to 6 persons, in which divers can be treated immediately after accidents. To these, mobile decompression chambers can be clamped on by flanges. They are transported if necessary (e.g. by SAR helicopters in low-altitude flight) to Kiel, to the largest pressure chamber of the German Federal Navy, in which up to 12 people can be subjected to pressure, as a simulation of deep diving as part of training, or to treat decompression sickness. For this reason and due to the outstanding training, the number and the consequences of serious and deadly diving accidents with the mine clearance divers in the German navy are remarkably small compared to the comparable units in other countries. A component of the training is the Armed Forces boat driving licence and the training about naval underwater explosives. Afterwards the training takes place to troop leader in the context of the ship safeguard training. The members of the MiTaKp can participate in numerous special training courses beyond that. Most longer-serving mine clearance divers are qualified e.g. also as motorists BCE, helmet divers (nationally examined diver), the parachutist, and single fighter. The training and operational planning was aimed originally to defend against conventional and more unconventional underwater weapons in case of emergency in a possible confrontation of NATO with the Eastern Bloc.