Changes and comments

Changes and comments

About this website

This website is edited by Jan Risberg (principal author of NDTT 4th and 5th  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 in the sixth edition of the NDTT


The next edition will hold a bottom text on each page identifying the edition/Revision. (Rev A)


A short description of  adjustments introduced in the NDTT relative to the original US Navy Diving Manual Rev 7 has been provided. (Rev A)

Diving at altitudes above 250 m

The flowchart has been revised to correct for an error related to N2 group addition for short acclimatization to height (corrrect value 7h10 min rather than 16h as presented in the previous flowchart) (Rev F).

Flying after diving

Serial 9, second sentence shold read: "The rules for flying after diving should be respected for all exposures to heights exceeding 1750 m asl.

Serial 12, the text in Ed 5 last paragraph should read (changes marked in bold types: "The diver has a Repetitive Group Designator of “B” from the preceding dive giving a penalty of 15 min to the 18m table. The repetitive group designator should be calculated for a bottom time of 35 min (15 min penalty + 20 min actual bottom time). A 35 min bottom time at 18 m will cause a Repetitive Group Designator of “F”."  (Rev B)

Multilevel diving

There are a number of printing errors in the Norwegian version of the multilevel diving tables (serial 9). 

Page 17, Serial 4, fifth bullet: The dive should be completed with a 3 min safety stop.... (Previous edition "5 min") . The examples (serial 7 and 8) have been corrected with respect to the length of the safety stop (Rev G).

Oxygen toxicity

A spelling error ("OUT" rather than "OTU" has been corrected in Serial 9. (Rev D).
The example (serial 12) provided incorrect decompression advice as decompression was based on a table depth of 30 msw rather than the correct 24 msw EAD. This in turn affected the total OTU calculation since 12 m decompression is 15 min rather than 30 min as suggested in Rev 5 (Rev G)

Standard air decompression tables

We have received a suggestion of inclusion of a formula/equation or alternatively a seaparate table that will allow preparation of no-decompression dives for smaller depth increments than 3msw. A practical example:  Maximum allowed bottom time for a no-decompression dive according to the 15 msw table depth is 90 min. The similar no decompression time for 18 msw table depth is 60 min. If the diver plans for a dive to 16 msw he/she will be restricted to a bottom time of 60 min for such a dive. However, if the bottom time is calculated as a linear interpolation, a bottom time of 80 min would be acceptable. The authors have not taken a position to this request, but we would appreciate any comment as to the operational use for a separate table for no-decompression dives rated in 1 msw steps in table depth.

SurDO2 tables - working depths shallower than 12m

We have been questioned regarding correct decompression procedures in the event that there is a need for work at shallow depths at the end of a SurDO2 dive. If the bottom time call for a an in-water decompression stop (12m or deeper) work would not be allowed at shallower depth. However, for those dives where no in-water staged decompression stop is called for, the diver may finish the dive at depths not shallower than 6m. Surface interval should start to run once ascent to surface starts. However, for some of the long bottom times, work shallower than 12m is prohibited. These bottom times are indicated by italic typeset in the SurDO2 table. (Rev C)

Prevention of Decompression sickness

We have received a comment regarding categorization of physcial activity (Serial 8 and 9, page 65-66). Should a streneous dive automatically call for extension of decompression time independent of presence of other risk factors? And should we simplify categorization of workload with "Low or medium" giving a score 1 and "High" a score 2?

Deep chamber dives

Rate of ascent (decompression rate) has been changed to 10 msw/min between the staged decompression stops to ensure a unified decompression rate throughout the publication.  (Rev E)

Procedures in the case of omitted decompression or uncontrolled ascent (+last page)

We discovered 1.11.19 that a printing error has caused page 109 and 110 to be incorrect. Page 109 holds the procedures in the case of omitted decompression or uncontrolled ascent, while the very last page only holds the ISBN number. Corrected pages can be downloaded here. The printshop has now (Dec 2019) replaced page 109 with the correct one..


The authors were approached aug 2019 by the Norwegian Oil and Gas Association, Forum for diving and subsea intervention. We were asked whether we could provide standardized tables for TUP-diving (transfer under pressure). The authors presented a draft revision of the TUP tables  on the Bergen International Diving Seminar autumn 2019. In December 2019 a report was submitted to the Norwegian Oil and Gas Association intended for further discussion. Please be aware that as per jan 2022 this report is available in Norwegian language only but it is on process of translation into English. The report holds a draft set of TUP-tables, but these tables have not yet been included in the Draft Rev 6 og NDTT.

Emergency decompression procedures

We have drafted a set of emergency decompression procedures. These are regrettably only available in Norwegian language and has not reached a sufficient status to be included in the draft of the 6th edition. 


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.