Triggers of Dive Accidents

[WVMike]

I just asked Errol ( a dive buddy of mine who is a GUE instructor here in South Florida) if he would write something up on the GUE concept of this....
Here is Errol Kalayci's explanation: ... " If one accepts that every dive done is a decompression dive as some amount of on gassing will occur when you descend, then you have taken the first step towards understanding “Minimum Decompression”. Minimum Decompression may be understood that for any dive, not requiring staged decompression, you should ascend in a controlled horizontal position at the prescribed table rate (usually approximately 30fsw/minute) up to your first stop. The first stop is set at 50% of depth. Your stops are all one minute in length and occur from that point, then every 10fsw up to the surface. By example, on a dive to 100fsw, a diver following Minimum Decompression would stop at 50fsw for 1 minute, then 1 minute at 40fsw, 1 minute at 30fsw, 1 minute at 20fsw, 1 minute at 10fsw. Which if you look at the profile what you see is that the typical 3 to 5 minute “safety stops ” are really just spread across the water column.

Clarification please.

For a 100fsw dive, my ascent is 30fpm to 50fsw; do I then stop at 50fsw for one minute and then continue?

Do I then travel to 40fsw at 30 fpm for 20 seconds and then stop at 40fsw for one minute before continuing on to 30fsw?

Or do I do a slow ascent from 40 to 30, total ascent time plus stop time to equal 1 minute? Then 1 minute ascent time, including travel and stop time for each 10fsw?

Or is it, 20 second ascent time and 1 minute stop per 10fsw?

 

[flots am]

Although I love a hijack as much as the next person, do you realize that you're all arguing about obscure technical details and the merits of procedures that require periodic training, when the average vacation diver doesn't even remember which way the tank valve is supposed to face?

A C-Card that expires if it's been more than a year since the last dive and requires re-certification would go a long way to reducing accidents.

flots.

 

[danvolker]

Clarification please.

For a 100fsw dive, my ascent is 30fpm to 50fsw; do I then stop at 50fsw for one minute and then continue?

Do I then travel to 40fsw at 30 fpm for 20 seconds and then stop at 40fsw for one minute before continuing on to 30fsw?

Or do I do a slow ascent from 40 to 30, total ascent time plus stop time to equal 1 minute? Then 1 minute ascent time, including travel and stop time for each 10fsw?

Or is it, 20 second ascent time and 1 minute stop per 10fsw?

Even though you may be pulling my leg with this, the answer is....
You swim up to 50 feet at 30 feet per minute....you stop for a minute, then your swim up ten feet is not really far enough to time it...just swim to 40 and stop for a minute.....then just swim to 30, etc.

It wont' hurt anyone to try this....the idea is, you can feel better after a dive with less bubbling...this should make most divers bubble less, so most will feel better and be less tired.
If you want to enjoy activities AFTER diving, then anything we can do to keep fresh for afterward is worth trying.

I don't think this is tech overkill..I think this is good for recreational divers to try, and it should help them understand better about what is going on in their tissues and blood.

REgards,
DanV

 

[WVMike]

Even though you may be pulling my leg with this, the answer is....

Dan, thanks for answer, not pulling your leg, maybe splitting hairs. I agree with you and have been practicing minimun deco. I followed the 1 minute per 10 feet scenerio. My main diving area has a very gentle slope from 40 to 10 feet and you can actually take a minute to swim from 40 to 30 feet along the bottom.

I have been using the stop watch feature on bottom timer and when I leave a stop reset it and then leave the next stop at one minute.

 

[Thalassamania]

Dan, thanks for answer, not pulling your leg, maybe splitting hairs. I agree with you and have been practicing minimun deco. I followed the 1 minute per 10 feet scenerio. My main diving area has a very gentle slope from 40 to 10 feet and you can actually take a minute to swim from 40 to 30 feet along the bottom.

I have been using the stop watch feature on bottom timer and when I leave a stop reset it and then leave the next stop at one minute.

Then you are ascending slightly faster than you should. Time between stops should be (1 minute stop time) + (20 seconds travel time) = 1 minute, 20 seconds, not just one minute of travel time.

 

[Akimbo]

Assuming you have an accurate way to measure the 250 psi in the larger tank. As mentioned above, the potentail inaccuracy of pressure gauges at the extreme ends is an issue.

On paper they are (close) to the same, but in reality, your mileage may vary.

Although typical mechanical analog SPGs accuracy is in the 3% full scale range, pressure transducers used in most integrated computers are ¼%. A lot of folks use them for partial pressure mixing. Take 5000 PSI as example of full scale; that is 150 versus 12.5 PSI.

 

[MXGratefulDiver]

Then you are ascending slightly faster than you should. Time between stops should be (1 minute stop time) + (20 seconds travel time) = 1 minute, 20 seconds, not just one minute of travel time.

I do it a bit differently ... 30 seconds travel time + 30 seconds stop time for a total ascent rate of 10 feet per minute.

Seriously, folks, the whole point of the exercise is to slow your ascent rate as you get shallower so as to give your fastest tissues a chance to offgass effectively.

Whether you do that as Dan, Mike, Thal or myself do it is rather inconsequential in the overall scheme of what's going on inside your body. Frankly, between the four of us, I doubt your body would know the difference which method you chose ...

... Bob (Grateful Diver)

 

[danvolker]

I do it a bit differently ... 30 seconds travel time + 30 seconds stop time for a total ascent rate of 10 feet per minute.

Seriously, folks, the whole point of the exercise is to slow your ascent rate as you get shallower so as to give your fastest tissues a chance to offgass effectively.

Whether you do that as Dan, Mike, Thal or myself do it is rather inconsequential in the overall scheme of what's going on inside your body. Frankly, between the four of us, I doubt your body would know the difference which method you chose ...

... Bob (Grateful Diver)

I totally agree. We use this as a "concept" in this discussion thread........Afterall, we were argueing about blowing safety stops and "bubbles of death"

Regards,
DanV

 

[Thalassamania]

All that I'd add to what Bob said is to not forget the idea of variable ascents rates with faster rates down deep and slower ones shallower.

 

[lamont]

Then you are ascending slightly faster than you should. Time between stops should be (1 minute stop time) + (20 seconds travel time) = 1 minute, 20 seconds, not just one minute of travel time.

you say potato...

GUE's _language_ for describing stops are that travel time is included in stop time so that 1 minute stops are approximating a constant 10fpm ascent rate.

this resolves the problem of what you do when you do a 45 second move -- in the GUE world you do a 15 second stop and then move again in order to hit the 10 fpm ascent rate. running through a decompression algorithm you're going to see negligible differences between 30 second move / 30 second stop vs. 20 second move / 40 second stop vs. 45 second move / 15 second stop. on the other hand, if you repeat enough 45 second moves + 1 minute stops it will not be the same deco as 20 second move + 1 minute stops.

if that isn't enough deco, then in the GUE world you lengthen the 'stop' time to 1m30s or 2m or whatever. the 30-second-move-30-second-stop procedure is baked in to GUEs concept of minimum deco being 1 minute stops from 50% of max depth, however.