Quiz - Equipment - NDL

[Rollin]

Measure with a micrometer, mark with chalk, cut with an axe.

That's the theory of decompression. Computer is the micrometer, diver being the chalk and the algoritm is the axe.
It is not about the micrometer not being precise enough.

 

[rongoodman]

None of the above. As other posters have pointed out, the uncertainty arises not from the measurements, but from the models used and how they might relate to a particular individual on a particular dive.

 

[Angelo Farina]

For me the point is another. Thrusting that staying just within the edge of NDL ensures to be allowed to resurface without any deco is dangerous, and should be avoided.
The safe approaches are only two:
- plan a no-deco dive with limits much more conservative than NDL
- plan a deco dive with all the required planning, training, equipment and procedures.

Staying too close to the edge of NDL is dangerous, no matter if this is due to your instruments, your body, or faults in the theory which attempts to explain their interaction.

 

[Celt]

To blindly follow NDL dive tables or a computers is a receipt for disaster. The pressure-time equation (which all tables and computers are based on) doesn’t contain enough information to safely bring all divers back to the surface at all times. I prefer to listen to what my body is telling me.

 

[tursiops]

To blindly follow NDL dive tables or a computers is a receipt for disaster. The pressure-time equation (which all tables and computers are based on) doesn’t contain enough information to safely bring all divers back to the surface at all times. I prefer to listen to what my body is telling me.

You must have extremely good hearing.....

 

[Celt]

You must have extremely good hearing.....

I think it’s more about feeling than hearing I’ve lost track of the amount of times that I’ve been half way back to the first stop when my arms felt heavy after a particularly hard dive but I will always slow and add a little more deco, I will also rub down my arms and legs while on the stops.

 

[rhwestfall]

choice should be e: tissue models

 

[ToneNQ]

I expect the true issue here is a 'sport diver' understanding of physiology and with basic equipment and skills. The question is a crude manner of giving an OW student a clear guide to not dive the NDL and expect to not get on the wrong side of the margin of error. Safe diving based on instruments and tables that are mathematical representations of observed and measured experiments/treatments, requires a lot more than the instruments and the tables.

Divers should avoid the NDL until they have the knowledge to plan a deco dive, the equipment to manage it and skills to execute it.

 

[Steve_C]

There is a margin if you are at NDL it is just less then if you are less than NDL. You can have different divers who are at different NDL at the same time and on the same gas. Different algorithms. If at depth you ride NDL for a bit because it is an interesting dive and then do a careful ascent you will be way under NDL by the time you get to your safety stop.

And what is riding NDL? 1 minute. 0 minutes? 5 minutes? If you hit 1 minute, rise 10 feet and are several minutes under have you ridden your NDL?

My point is not that NDL is not important but rather that it is fuzzy line that lets you know you are eating up more of your safety margin but your safety margin is not gone. You need to take that into account and act accordingly.

 

[TMHeimer]

I agree with Angelo about being unsafe if close to the NDL, which we all should know. I guess you could also say that since we don't know everything about DCS, you can get the bends even if well within limits (as we're always told...), but that's a little far from the question.
Actually, I LIKE the question. My first thought is that any instrument can be out of whack, by a little or even by a lot, so it's "all of the above". I recall my SPG getting stuck on 1000 PSI once (replaced it of course). I guess a depth gauge can get stuck on say 100', or start to react slower to depth changes? I don't know. My compass cracked & broke once. Perhaps a DC has less chance of being off (unless it floods & craps out, of course), but I would imagine there could be a rare instance for that too.
I thought the question was clear and a "gimme".
Again, we can argue small points here, but we all probably understand what they're asking.