procedure so that the instruments are cleaned and potentially maintained in chronological succession the chronological offset may be seen from the pulse time diagram of fig8 that shows the chronological course of the valve connections for the various agents of air and water for the four instruments referenced 11 14 a high cleaning efficiency given a low water consumption is achieved with this chronologically successive cut in of the agents the cassette 12 is charged with instruments and the instruments that have movable internal parts such as the angle pieces turbines sprays or the like are plugged onto corresponding adapters 16 of which a maximum of four are allowed in the cassette the other instruments are placed at a holder device above the floor of the container the cassettes are then closed by putting the upper cassette part 12b on the lower part 12a and the cassette is introduced into the chamber 2 of the apparatus during this insertion the rear cover 20 is lifted and as a result thereof the nine nozzle arms 3 extend through the bores 17 of the backwall 15 of the cassette after the cassette has been inserted into the chamber to such an extent that the connection of lines 41 and 42 with the connectors 39 and 40 see fig6 has been produced the cover 5 of the apparatus is closed and the apparatus is turned on after a self test which lasts approximately half a minute a cold cleaning of the instruments occurs utilizing cold water which is supplied to the adapter 16 and to the nozzle arms 3 via leads 9.