Proposal for new terminology

[Rick Murchison]

I am seeking proposals for some new terms.
Today the literature is peppered with inaccurate terminology - the ones I want new terms for here are "No-decompression Limit," No-decompression diving," "NDL" and so forth.
Every dive is a decompression dive - and there are procedures for handling decompression on each and every dive, whether it be a simple ascent rate specification or a combination of ascent rates, stops, gas switches and chamber schedules taking days - and everything in between.
Keeping it simple (always one of my goals) I propose we push for a replacement to the "No-decompression" term to "No-Stop" limit, dive, adjusted time etc.
I seek your suggestions.
Thanks,
Rick

 

[JamesK]

Well, technically every dive, even if at a NDL, should include a 3-5 minute "safety stop". This in effect is a decompression, although very minimal. Maybe a "minimum decopression limit", MDL, would be more appropriate.

 

[daylight]

Rick,

I agree 100% with your characterization. I imagine the terms "No Decompression" and "Safety Stop" were selected for marketing appeal more than being descriptive. They want potential customers to believe that this sport is "No Risk". I wish your terms could be adoopted or at least more widely used to more accurately describe reality.

FWIW.

Larry

 

[SubMariner]

Every dive is a decompression dive - and there are procedures for handling decompression on each and every dive, whether it be a simple ascent rate specification or a combination of ascent rates, stops, gas switches and chamber schedules taking days - and everything in between.

I do not believe this is accurate. By definition, recreational diving is no decompression diving because if a diver adheres to the NDL limits, then he/she can make a direct ascent to the surface. Making a safety stop at 15' is "recommended" to add a margin of safety, as is a slower ascent rate (eg; 30 fpm as opposed to 60 fpm).

It is only when a deep dive is made that agencies mandate making a safety stop at X feet for X number of minutes. Or when a diver violates the NDL limits, then there are procedures to be followed because the dive is no longer considered a proper NDL dive.


~SubMariner~

 

[Rick Murchison]

Originally posted by SubMariner


I do not believe this is accurate. By definition, recreational diving is no decompression diving because if a diver adheres to the NDL limits, then he/she can make a direct ascent to the surface. Making a safety stop at 15' is "recommended" to add a margin of safety, as is a slower ascent rate (eg; 30 fpm as opposed to 60 fpm).

It is only when a deep dive is made that agencies mandate making a safety stop at X feet for X number of minutes. Or when a diver violates the NDL limits, then there are procedures to be followed because the dive is no longer considered a proper NDL dive.


~SubMariner~

So, you can make an instantaneous no-limits ascent to the surface at, shall we say, 360 fpm (about as fast as the normal diver can swim)??? If not, why not? It is because your decompression protocol (to prevent decompression injury) for your so-called "no-decompression" dive is a 30FPM rate of ascent. Every dive is a decompression dive. As a point of fact, *every* decompression protocol could be expressed as a [variable] rate of ascent rather than stops - we use stops because they are easier to control than a rate of ascent schedule. The no-decompression term is misleading and confusing. Your post proves it!
Rick

 

[Spectre]

I've always liked the term no-stop ascent diving. This doesn't really cause issue with the safety stop, because it's "recommended" rather than "required", so safety stops are still included in no-stop ascent diving. If you hit the table limits and are then required to do the 5 min stop, then you of course have gone beyond no-stop diving and your into a required decompression stop...

-Jeff

 

[JamesK]

If on the dive you are doing, you could possibly suffer from DCS, then it is a decompression dive, IMO.

 

[Uncle Pug]

Originally posted by SubMariner


I do not believe this is accurate. By definition, recreational diving is no decompression diving because if a diver adheres to the NDL limits, then he/she can make a direct ascent to the surface. Making a safety stop at 15' is "recommended" to add a margin of safety, as is a slower ascent rate (eg; 30 fpm as opposed to 60 fpm).

It is only when a deep dive is made that agencies mandate making a safety stop at X feet for X number of minutes. Or when a diver violates the NDL limits, then there are procedures to be followed because the dive is no longer considered a proper NDL dive.


~SubMariner~

Dear Sub,
Definitions do not create reality....
Often they do not even reflect reality....
Rick is right....

As for your statements... you are also right:

A diver adhering to the so called *NDL* can indeed ascend directly to the surface as can a diver with a huge decompression obligation.

However survival without impairment is another matter all together. You cannot take a max NDL gas load directly to the surface without incurring damage.

Your faith in the *agencies* commandments not withstanding.

Ever heard of an *Undeserved Hit*?
Even though there is no such thing as *undeserved* the hit is real enough.

 

[Uncle Pug]

Originally posted by Rick Murchison
I am seeking proposals for some new terms.

I propose we push for a replacement to the "No-decompression" term to "No-Stop" limit, dive, adjusted time etc.

I seek your suggestions.

Well you already know that I agree with you Rick however I don't think....:
1. ....there is any chance that folk like us are going to change things but shoot no harm in pretending.
2. ...."No-Stop" is any better than "No-decompression" since it implies (or at least could be construed to imply) that direct immediate ascent with out damage is possible.

Why not just eliminate (since we are pretending that we can change things) the moronic acronym NDL and replace it with nothing. Tell folks up front that every dive is a deco dive and every dive has a minimum deco to be followed. Any direct immediate ascent for emergency purposes poses a risk of clinical or at least sub-clinical DCS. Truth is seldom conducive to marketing so I think this has no chance of happening at all.

 

[rcohn]

Originally posted by Uncle Pug

A diver adhering to the so called *NDL* can indeed ascend directly to the surface as can a diver with a huge decompression obligation.

However survival without impairment is another matter all together. You cannot take a max NDL gas load directly to the surface without incurring damage.

Your faith in the *agencies* commandments not withstanding.

Ever heard of an *Undeserved Hit*?
Even though there is no such thing as *undeserved* the hit is real enough.

Divers have been ascending directly to the surface for years with a full NDL gas load. The old Navy tables had longer NDL limits, with a 60 fpm direct ascent to the surface. I believe the Navy statistics have shown around a 2% hit rate when the tables were used to their maximum limits. This means that a Navy diver (relatively young and fit) could remain at depth to the NDL then directly ascend to the surface with a 98% chance of being fine. Note the hit rate for normal (not to max limits) usage of the tables was much lower.

Am I advocating direct ascent to the surface, of course not. Ascents should be slow and include safety stops. I simply believe the risks should not be blown up way out of proportion

If you want to bring up silent bubble damages, what are your references? I’m not aware of any studies that have demonstrated clear links to damage in sport divers who haven’t suffered DCS hits. Commercial diving has different issues. If you’re about to bring up the red blood cell rigidity theory I’ll point out in advance that this is another case where the tech diving gurus are just making it up. There is no credible scientific evidence that this is an issue for sport or technical divers.

I see two serious problems with the all dives are decompression dives mantra.

1. If all dives are decompression dives, and diving is safe, then decompression diving with mandatory stops is no more dangerous than no stop diving. Don’t laugh, I’ve seen this argument made online in the past. This leads recreational divers to believe they can casually begin decompression diving with no additional training or planning. After all, all dives are decompression dives, right?

2. Many divers begin to believe that safety stops are an absolute necessity, skip it on a NDL dive and they will probably be bent. This leads to questions like, “if I’m bringing an unconscious diver to the surface, should I stop for 3 minutes at 15 ft?” Again don’t laugh, I’ve seen this asked several times. A main point of NDL diving is that direct ascents may be carried out with a reasonable margin of safety in emergencies. The over-exaggerated assessment of the risks that has become popular obscures this fundamental concept.

I don’t really care whether we call it no decompression or no stop diving, but the risks and issues should be presented in an accurate and balanced manner.

Ralph