Unknown Tourist dead, Dive Master ill - Ambergris Caye, Belize

[boulderjohn]

The two great dangers in scuba are (in order of importance) lung overexpansion injury and decompression sickness. We tell new students that the number one rule in scuba is "don't hold your breath," but that is pretty much the extent of the training for the biggest danger. With DCS, we fill them with absolute terror. How many times on ScubaBoard have we seen threads started with something along the lines of "Two months ago I did a 60 foot dive for 20 minutes, and this morning I am feeling a little dizzy? Is this DCS? Should I go immediately to the chamber?"

While diving in the Galapagos years ago, my buddy (certified as a DM but not practicing) started a panicked sprint to the surface. To make a long story short, when I finally caught up with him, he was in stark terror. He had looked at his computer at depth and seen he had only two minutes of NDL left, and because he knew that going into deco would likely kill him, he risked a fatal lung overexpansion injury so he could get to the surface as quickly as possible.

 

[also_anon_dc]

He had looked at his computer at depth and seen he had only two minutes of NDL left, and because he knew that going into deco would likely kill him, he risked a fatal lung overexpansion injury so he could get to the surface as quickly as possible.

The fact that someone could go through DM training and still think this is the correct action when seeing you have 2 minutes on your NDL is beyond my comprehension.

 

[Steelyeyes]

The fact that someone could go through DM training and still think this is the correct action when seeing you have 2 minutes on your NDL is beyond my comprehension.

Just make a normal ascent for 20 feet and wait for the computer to show you what your new NDL is. Done it many times. Panic is the real killer.

 

[Outbound]

The PADI RDP clearly states that a safety stop is required any time the diver comes within three pressure groups of the NDL and for any dive to 100 feet or greater. So yes, for most diving a safety stop isn’t technically required. But for the above situations skipping one theoretically puts the diver on the wrong side of the risk curve for DCS.

 

[OMyMyOHellYes]

The PADI RDP clearly states that a safety stop is required any time the diver comes within three pressure groups of the NDL and for any dive to 100 feet or greater.

What is a PADI RDP?

 

[Outbound]

What is a PADI RDP?

PADI tables. AKA: Recreational Dive Planner.

 

[tursiops]

Info - History of the Safety Stop

There have a number of threads recently on ScubaBoard that refer to a Safety Stop, and some assertions as to how it came about and when. Here is what I can find on this topic; it would be nice to flesh it out so myths and speculation can be minimized! And always remember the research has been...

scubaboard.com

Safety stops are suggested, not required.

Depends on the dive profile.

I wonder if training about Safety Stops has become overzealous to the point that people are terrified of missing them.

Some countries mandate them. Cayman Islands, for example.

There were no safety stops in my 1980 training. "The PADI Open Water Manual recommended safety stops in the 1984 edition. The 1988 release of the Recreational Dive Planner introduced safety stops to a wider audience. This step, along with PADI’s “S.A.F.E. Diver” campaign, was a big help in educating divers. Slowly Ascend From Every Dive became an acronym dive instructors passed along to new students."

See History link above.

I think many people, including professionals, have been led to believe they will die a horrible, painful death if they skip a safety stop on any dive.

One of nice things about modern computers like the Shearwater is the SurfGF feature, which allows you to know what percentage of a supposedly safe ascent you would be in if you were to surface immediately. I have seen DMs signal a safety stop after dives when we were in the 30s for SurfGF. The max I saw was the dive with CocoView in Roatan where we never once got my SurfGF above 19. Yep, the DM signaled for everyone to do a safety stop. (When I dived with CocoView, we rarely initiated a safety stop with SurfGFs above 50; they just wanted to make sure there wasn't even an infinitesimal chance of DCS.)

The SS served a purpose. The Surf GF addresses the same issue, with tools not available when the SS was invented. It is a better solution to the problem.

The downside of the SS is that people think the dive is over when the three minutes are up, and rocket to the surfac.e

Our rescue training when I did my Divemaster course in 1981 didn't include a safety stop.

See History link above.

Nor in my 1986 NAUI/YMCA training.

See History link above.

The PADI RDP clearly states that a safety stop is required any time the diver comes within three pressure groups of the NDL and for any dive to 100 feet or greater. So yes, for most diving a safety stop isn’t technically required. But for the above situations skipping one theoretically puts the diver on the wrong side of the risk curve for DCS.

SurfGF is even better, but not everybody has it.

 

[MidOH]

The two great dangers in scuba are (in order of importance) lung overexpansion injury and decompression sickness. We tell new students that the number one rule in scuba is "don't hold your breath," but that is pretty much the extent of the training for the biggest danger. With DCS, we fill them with absolute terror. How many times on ScubaBoard have we seen threads started with something along the lines of "Two months ago I did a 60 foot dive for 20 minutes, and this morning I am feeling a little dizzy? Is this DCS? Should I go immediately to the chamber?"

While diving in the Galapagos years ago, my buddy (certified as a DM but not practicing) started a panicked sprint to the surface. To make a long story short, when I finally caught up with him, he was in stark terror. He had looked at his computer at depth and seen he had only two minutes of NDL left, and because he knew that going into deco would likely kill him, he risked a fatal lung overexpansion injury so he could get to the surface as quickly as possible.

Yeah, scuba could really stand to teach the science better.

Don't panic, needs added to the list.

 

[Steelyeyes]

Info - History of the Safety Stop

There have a number of threads recently on ScubaBoard that refer to a Safety Stop, and some assertions as to how it came about and when. Here is what I can find on this topic; it would be nice to flesh it out so myths and speculation can be minimized! And always remember the research has been...

scubaboard.com

Depends on the dive profile.

Some countries mandate them. Cayman Islands, for example.

See History link above.

The SS served a purpose. The Surf GF addresses the same issue, with tools not available when the SS was invented. It is a better solution to the problem.

The downside of the SS is that people think the dive is over when the three minutes are up, and rocket to the surfac.e

See History link above.

See History link above.

SurfGF is even better, but not everybody has it.

Those are all great points. So to relate them back to this incident was it prudent to attempt the safety stop given the previous dive profile or just take the ailing diver in a controlled manner directly to the surface?

As to the person that died, from the best I can tell he was below the ailing diver, then above at or near the surface, and then found on the bottom. Given the description of him upon recovery it seems like an extreme buoyancy issue, maybe stuck inflator, caused the rapid ascent. Somehow he became negative once on or near the surface but understandably all attention had been on the person that survived so it's hard to really know.

 

[firemedic521]

I want to jump back in to discussion of testing air. I'm a new diver but a longtime Hazmat technician. There are many inexpensive ( Less than $50 )Carbon Monoxide detectors available that are designed for use in the home with digital displays but should work well for checking for the presence of CO in dive tanks. one thing to note is these detectors are passive detectors meaning the air is not being actively pumped across the sensor. You will need to contain the air in something and put the detector inside. I would put the detector in a small trash bag then inflate the bag from the tank and tie it off. Let the detector sit in the sealed back for a minute and see if you get any readings.