Diving with gradient factors for a new recreational diver

[boulderjohn]

I remember seeing some DCS research in which they observed the large portion of cases to be related to medium tissues. If I remember right, diving buhlmann, no idea what profiles. Definitely an area for future research. Might be useful to adjust the safe limits for those tissues.

I am pretty sure I know the study to which you are referring. The idea that it is obvious is contradicted by a once popular thought that the key to avoiding DCS was protecting the fast tissues, and if you did that, you did not have to worry about slower tissues. You will still find people saying that, often quoting one famous advocate of that theory.

That same study strongly suggested that nearly everyone doing NDL dives does so within limits--or at least believes they do. That explains why a large percentage of DCS cases happen with people who dive within limits--or at least think they do. (See my next post.)

 

[boulderjohn]

I was doing a series of dives working with students in several advanced classes. I would work with one class, then switch to another for the next dive, etc. While I was doing this, the people who were not in classes would dive on their own.

At then end of one of the dives, when we surfaced, one of the divers who was not in the class for that dive surfaced at the same time we did. He announced that his computer had started acting weird on that dive. It said something unusual, and then instead of counting down the NDL, it started counting numbers up. What was up with that? I immediately asked him what number he ended up with, but he had not checked recently and didn't know. I took him down to safety stop depth. Looking at his computer, I saw that it was in error mode. We stayed 15 minutes. I took him up to the surface and had him breathe oxygen for a while to be safe. He was OK.

Yes, you need to know what a computer is doing if you use one. One thing you should know is when it is giving the length of a required deco stop if you violate NDLs.

Years ago we used to think the proper thing to do in OW training was to teach students how to use tables and then send them out into the diving world knowing they will not use those tables and will instead buy a computer, with no instruction on how computers work.

 

[scubadada]

I recently did 45 dives in 13 days in Bonaire. By the end of the 2 weeks, there was residual nitrogen in some of the longer compartments for a time. Sorry, no photos.

What you would really like to see is a graph of nitrogen loading of various compartments over the duration of a dive sequence, as is shown in the article describing the development and validation of the DSAT/PADI RDP. This sequence is 4 dry dives per day for 6 days to the limits of the RDP.

 

[doctormike]

I was dong a series of dives working with students in several advanced classes. I would work with one class, then switch to another for the next dive, etc. While I was doing this, the people who were not in classes would dive on their own.

At then end of one of the dives, when we surfaced, one of the divers who was not in the class for that dive surfaced at the same time we did. He announced that his computer had started acting weird on that dive. It said something unusual, and then instead of counting down the NDL, it started counting numbers up. What was up with that? I immediately asked him what number he ended up with, but he had not checked recently and didn't know. I took him down to safety stop depth. Looking at his computer, I saw that it was in error mode. We stayed 15 minutes. I took him up to the surface and had him breathe oxygen for a while to be safe. He was OK.

Yes, you need to know what a computer is doing if you use one. One thing you should know is when it is giving the length of a required deco stop if you violate NDLs.

Years ago we used to think the proper thing to do in OW training was to teach students how to use tables and then send them out into the diving world knowing they will not use those tables and will instead buy a computer, with no instruction on how computers work.

Strong work!

Much better than something that I once saw in the Caribbean. Diver surfaced with their computer "beeping", and couldn't figure out how to turn the alarm off. One of the instructors tied it to a reel and dropped it into the water for a while until the noise stopped.

 

[Wibble]

I was dong a series of dives working with students in several advanced classes. I would work with one class, then switch to another for the next dive, etc. While I was doing this, the people who were not in classes would dive on their own.

At then end of one of the dives, when we surfaced, one of the divers who was not in the class for that dive surfaced at the same time we did. He announced that his computer had started acting weird on that dive. It said something unusual, and then instead of counting down the NDL, it started counting numbers up. What was up with that? I immediately asked him what number he ended up with, but he had not checked recently and didn't know. I took him down to safety stop depth. Looking at his computer, I saw that it was in error mode. We stayed 15 minutes. I took him up to the surface and had him breathe oxygen for a while to be safe. He was OK.

Yes, you need to know what a computer is doing if you use one. One thing you should know is when it is giving the length of a required deco stop if you violate NDLs.

Years ago we used to think the proper thing to do in OW training was to teach students how to use tables and then send them out into the diving world knowing they will not use those tables and will instead buy a computer, with no instruction on how computers work.

What did his backup computer say when his primary was saying "don't ask me mate, ask the other one"?

A backup computer is as important as backup gas, buoyancy, SMBs, etc.

 

[scubadada]

...Yes, you need to know what a computer is doing if you use one. One thing you should know is when it is giving the length of a required deco stop if you violate NDLs...

I have told this story on SB previously. I do about 100 dives off charter boats in SE Florida each year, often with some divers who do not know much about their computers, like having to ask how to set the nitrox. Several times each year I'm asked why someone's computer is not working correctly. The most common answer is that the computer is in violation gauge mode for having missed a decompression stop. They often look at me incredulously.

 

[doctormike]

What did his backup computer say when his primary was saying "don't ask me mate, ask the other one"?

A backup computer is as important as backup gas, buoyancy, SMBs, etc.

How do you figure?

If my primary gas source fails, I need a redundant gas supply to end the dive safely. If my primary source of buoyancy fails, I may need a backup to end the dive safely.

If my computer actually fails (we are talking about NDL dives here), all I need to do to end the dive safely is to surface, right? Of course, the computer of the diver in John's story didn't fail, it was trying to save his life.

If you don't understand how your DC works, a backup won't help.

 

[tursiops]

I have told this story on SB previously. I do about 100 dives off charter boats in SE Florida each year, often with some divers who do not know much about their computers, like having to ask how to set the nitrox. Several times each year I'm asked why someone's computer is not working correctly. The most common answer is that the computer is in violation gauge mode for having missed a decompression stop. They often look at me incredulously.

And I'll bet many of those are Suuntos.

 

[tursiops]

If you don't understand how your DC works, a backup won't help.

Exactly!

 

[J-Vo]

Every new diver should watch this: