SSI Nitrox manual question?

[jj1987]

How does SSI round here?

Using the SSI equivalent air depth table, determine the equivalent air depth (ead) for the following depths using EAD36.

Dive 1: 90ft/27m EAD is __________
Dive 2: 80ft/24, EAD is __________.

My first thought is that you would go with the greater depth value of 94ft since that would error on the side of safety. However, the engineering student part of me decided that I should check the formulas and see how far off either answer would be.

Doing the math, the actual value would be
Dive #1- [(1-.36)*(90+33)/.79]-33 = 66.646ft
Dive #2- [(1-.36)*(80+33)/.79]-33 = 58.544ft

Now, dive 1 falls between 81ft and 94ft on the table, which have a EAD of 60 and 70ft respectively. Does the EAD formula have any room to round and stay safe already built in, or do you always go with the greater EAD? I couldn't find this information in the manual, as it uses round numbers for the example problems in the chapter. I also noticed that if you plug the max depths into the formula, you'll find that the EAD's are already rounded up to the nearest ten, but is this enough of a safety margin to be built in?

Sorry if it's a obvious or stupid question, I just hate the guy who doesn't have the correct answers on what's essentially a take home test in my classes here at UCF, so I don't want to be "that guy" in my dive class. The lecture is Wend, so I'll keep looking until then.


One other thing that baffles me, and I'll bring this up in lecture, so this is more to stir convo than an actual question I'm needing an answer for, is the SSI manual constantly says "But many nitrox divers do ______ for added safety" while talking about things like diving the air tables and such. Is this just a legal loophole if someone gets in trouble or what? I mean, why tell someone to use the dive tables, and then imply that they're not really safe...it's like saying a car can safely do 160, and you should use this car to go 160mph, but many people driving these cars still prefer to drive them like a mini van.

Other than that, I found the manual very well written, and much more clear than many technical books I've read. The dvd sucked, had a monotone instructor, and reinforced bad diving habits like dangling gear. Not to mention there wasn't anything I remember hearing on the dvd that wasn't in the book.

[caverkevin]

Diving air tables has always been a selling point of Nitrox. That you can keep the bottom times the same but reduce the DCS risk. Or you can use Nitrox tables, computer or the EAD formula to increase the BT, for a similar DCS risk compared to diving air. Some people do not like living near the edge of anything.

Cheers!!

Kevin

[SuPrBuGmAn]

All the courses will teach to round up to the next depth group for safety.

[jj1987]

All the courses will teach to round up to the next depth group for safety.

Thank you!