No deco

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The zero time is in a dive with a scuba set by the decompression table predetermined period of time in which one without decompression can return to the water surface (persisting for a certain time at a certain depth). However, all diving organizations recommend a three-minute safety stop at a depth of five meters, even when performing a no-stop dive.

When Scuba diving is the scuba tank compressed air (78.07% nitrogen , 20.96% oxygen , 0.93% argon , 0.04% carbon dioxide ) or other breathing gas mixture, such. B. Nitrox . The nitrogen in the breathing gas mixture is during the dive of tissue and blood was added to the diver and goes into solution in the body fluid. The greater the diving depth and thus the ambient pressure, and the longer the exposure time, the more nitrogen can dissolve in the body tissue. If the person resurfaces too quickly and the ambient pressure drops, the dissolved nitrogen can bubble out and form gas bubbles in the body. In order to be able to surface again without the risk of a life-threatening diving illness , the concentration of the nitrogen dissolved in the blood and tissue must not exceed a certain limit value . The no-stop time is the time until this value is reached.

The deeper you dive, the shorter the no-stop time. Depending on the breathing gas mixture and the decompression table used, the diver reaches the no-stop time at a certain depth sooner or later. A diver after exceeding the zero time lasts longer at the same depth or less, so that starts decompression to run. The decompression time indicates how long a diver should observe decompression stops while surfacing , which must be planned precisely so that the air supply is sufficient. If necessary, additional breathing gas sources are to be provided, which guarantee a safe ascent including the decompression stops.

The no-stop time can be extended by using breathing gas mixtures with a reduced nitrogen content (e.g. Nitrox ).

Individual evidence

  1. ↑ Divers FAQ. Why don't divers typically use oxygen? In: dive.steha.ch. Stefan Hagen, accessed on April 17, 2020 : “Pure oxygen becomes toxic from a depth of only 7 meters . Air is a gas mixture that only consists of 21% oxygen. "
  2. ↑ Thomas Kromp , Hans J. Roggenbach , Peter Bredebusch : Practice of diving . 3. Edition. Delius Klasing Verlag, Bielefeld 2008, ISBN 978-3-7688-1816-2 , p. 96-101 .
  3. ↑ Frank Ostheimer: decompression theory. (PDF; 2.2 MB) In: htsv.org. Hessischer Tauchsportverband eV , accessed on March 7, 2017 .