Quote Originally Posted by Jax View Post
NO. . . TDI did not change "their" Table. TDI's book, "Extended Range / Trimix", lists the new Navy table.

The fastest way to tell the difference is the new table does not have a 10fsw stop.

The question is not "why did TDI change", the question is "why such a huge difference"?



In the *old US Navy Air Decompression Table* a dive to 160fsw for 25 min had a deco obligation of 4:20 to first stop, to 7min @ 20fsw + 20 min @ 10fsw or a total deco of 32:20. You came out as a group K.

In the new US Navy Air Decompression Table, a dive to 160fsw for 25 min has a 4:20 ascent, a stop at 30 for 3 min, @ 20 for 49 min for a total deco of 49 min, and you come out as group N.

32 / 49 = 65%, which means deco is increased 35% over the old table.

Put another way, 49min is 153% of the old table.

What has changed to cause such a huge increase in conservatism?

Note - the only reason TDI came up at all is because the book problems, which one could plan perfectly well, within given parameters, on the old tables, were not doable within those parameters with the new table. One would need stage bottles to complete the dives.

By the way, in the new Navy dive table, if you over-stay your 25 minute dive at 160fsw, your deco obligation goes from 49:00min to 73:40 min.
It appears they have shifted the stops deeper to keep bubble size smaller. The outgassing will be slower, hence the longer decompression time.