Changes and comments

Nettstedet for Norske dykke- og behandlingstabeller

Changes and comments


About this website

This website is edited by Jan Risberg (principal author of NDTT 4th edition). It is constructed to be a link between the authors and readers of these tables. Corrections and comments to the tables will be formalized through publication of new revisions. In the time period preceding a revision, there will be discussion between the editors as well as professionals. This website will present suggestions for table changes. We sincerely appreciate comments to the tables: supportive, improvement proposals, inaccuracies a.s.o. Please send us an e-mail to allow us to follow up!


Topics discussed on this particular page of the website has not been approved/formalized and is not intended to replace recommendations of the last official edition of the table.The revision proposals available for download at the right hand panel, should not be used operationally.



Areas subject to revision or correction



Diving at Altitude above 250 m

The text describe limitations for travel to altitudes before diving and how to calculate decompression when diving at altitude. The tables do not satisfactory describe limitations for returning to sea level after a dive at altitude (typically With helicopter) or driving over a mountain area after diving at altitude. A possible solution has been presented in Rev A0


Standard Air Decompression Table

A request for listing of repetitive groups for bottoms time 5 min has been requested. This is relevant for multilevel-dives. In rev A0 such groups have been identified for 5 min bottom time for table Depths 36, 39 and 42m.

A "non" diving day (Serial 18) has been defined as as a surface interval of minimum 24 (Rev A9).



The example (Serial 4) was not appropriately designed with respect to diving depth causing pO2 to be excessively high. The depth has been changed to avoid this concern (Rev A5)



A question has been raised regarding the consequences of undertaking a dive to depths not exceeding 6m after a SurD-O2 dive. How should this affect the required minimum surface interval for the following SurD-O2 dive. In rev A0 it is suggested that the surface interval should be extended by the dive time of the preceeding shallow dive.


We have received feedback that some DDC are unable to decompress 10 m/min from 15 to 12 m. Section 8 has been rewritten to underscore that this rate (10 m/min) is the optimal rate, but a lower rate is acceptable. (Rev A4)


Page 62: "Total decompression time" has been misprinted for bottom times 70 and 80 min, should read 107 and 133 min. However, decompression stops and Oxygen breathing time is correctly stipulated. There are a few rounding errors (1 min) of listed total decompression times for some other Depth/bottom time combinations, but these do not affect decompression stipulations (water stops, Chamber oxygen breathing time). (Rev A7)


Page 64: The SurD-O2 table for 51m profile was printed inaccurately because the Depth of decompression stops were not identified. These should be 21, 18, 15 and 12m. The graphic layout has been modified to correct this ambiguity


Prevention of decompression illness

There may be situations in which extension of decompression, to accommodate for individual risk factors, may incur decompression according to a tabulated bottom time indicated as exceptional. There is, however, no need to shorten the actual bottom time to avoid this. (Correction suggested in Rev A3)


Procedures in the event of omitted decompression or uncontrolled ascent

The title was incorrectly and inconsistently translated from the Norwegian original text and has been changed. (Rev A6)


Emergency procedures

There are inconsistencies between the text and the flowchart. The recommendation for oxygen use is probably excessive. Rev A0 suggest simplifications.



In this panel you may download the latest internal draft/working document for the forthcoming table revision. This document is not approved for operational use. It is published to stimulate comments. The document has not been properly reviewed and layout is not finalized. This will typically affect Table of contents, location of figures and page shifts. Such errors will not be corrected until the final official revision has been published.