deco myths

[L13]

Possibly I did not explain well enough the reason for which I suggested a safety boundary of 10 minutes from NDL.

I was responding to @admikar . I understood what you were saying. I mostly wanted to point out that "X minutes" is not the same physiological safety margin for different dives , and with different GF High's, there could be counter intuitive safety implications.

 

[Angelo Farina]

I was responding to @admikar . I understood what you were saying. I mostly wanted to point out that "X minutes" is not the same physiological safety margin for different dives , and with different GF High's, there could be counter intuitive safety implications.

On this I entirely agree.
But, as said, I suggested 10 minutes as a time buffer accounting from some adverse circumstances causing a delayed ascent.
It is part of dive planning, it is not "deco conservatorism", which has akready been addressed with a proper choice of GF values (or, depending on the computer, with other conservatorism factors).
One should not confuse dive planning with deco conservatorism, so I thank you for making the distinction clear.
As said, I was not clear enough in my previous post, making @admikar confusing the two things.

 

[Tom_Ivan]

How do you keep from going crazy on a 60 minute deco stop? Sitting at 20 feet doing nothing for 3 minutes is hard enough for me!

Tech diving does not always mean long stops. Depending on the dive site, you can plan the profile so that the deco obligation is mostly gone before you start your final ascent. Then with 100% oxygen your stops can be very short indeed.

 

[Wibble]

Tech diving does not always mean long stops. Depending on the dive site, you can plan the profile so that the deco obligation is mostly gone before you start your final ascent. Then with 100% oxygen your stops can be very short indeed.

Or 80%. Or 50%. Or even nitrox 21

In any case, hanging around on a stop is very relaxing. Especially if you’ve got enough redundancy.

 

[ofg-1]

How do you keep from going crazy on a 60 minute deco stop? Sitting at 20 feet doing nothing for 3 minutes is hard enough for me!

You just make up little games to pass the time. As example, if you find some trash during the dive, see if you can tie it on your buddy without him noticing. Clip a dropweight on your buddy while hes not looking. See if you can hogtie him with his own reel. Steal his SMB. Zipties can be fun.

 

[admikar]

You just make up little games to pass the time. As example, if you find some trash during the dive, see if you can tie it on your buddy without him noticing. Clip a dropweight on your buddy while hes not looking. See if you can hogtie him with his own reel. Steal his SMB. Zipties can be fun.

I can see this quickly going down the "cut his hose" route

 

[Lorenzoid]

Tech diving does not always mean long stops. Depending on the dive site, you can plan the profile so that the deco obligation is mostly gone before you start your final ascent. Then with 100% oxygen your stops can be very short indeed.

I speculate that most "tech dives" done nowadays involve less than 30 minutes of deco. Seemingly everyone is at least dipping their toes into tech diving. People seek tech training when they realize they don't need to be confined to the somewhat arbitrary limits that have long circumscribed "recreational" diving, and want more flexibility. It would be interesting to know what percentage of "tech dives" are big dives with lots of deco.

 

[admikar]

OK, what is big deco? 20 minutes? 30? 60? 100?
One deco gas? 2? More?
If it's 100 and 2, I have never done a tech dive.
I consider tech dive if I need to hold more than 10 minutes at 3m. Deco that clears on my way up is not considered a tech dive.

 

[Angelo Farina]

OK, what is big deco? 20 minutes? 30? 60? 100?
One deco gas? 2? More?
If it's 100 and 2, I have never done a tech dive.
I consider tech dive if I need to hold more than 10 minutes at 3m. Deco that clears on my way up is not considered a tech dive.

Here in Europe we have training agencies, such as Cmas and Bsac, which always considered and still consider deco dives to be fully recreational.
Then a couple of US-based agencies started to push for a more restrictive definition of recreational diving, limiting the depth and the diving time and promoting instead the practice of doing several separate dives along the day. Which is more profitable for the commercial diving center...
But here in EU we continue to have a number of recreational divers, as me, who routinely plan and execute dives with some (short) mandatory deco stops.
Personally I consider recreational diving any dive down to 50 m max and with deco which you can plan and execute using a low-cost recreational computer, such as my Cressi Leonardo.
In my case this excludes accelerated deco with a different hyperoxygenated mix.
Which I use when available, but keeping the deco times the same as with the bottom mix.
Dealing with accelerated deco requires knowledge and equipment (computer) which I do not own.
And, from a scientific point of view, I am not fully convinced on those formulas employed for shortening the deco times...

 

[JMarc]

And, from a scientific point of view, I am not fully convinced on those formulas employed for shortening the deco times...

Could you expand on that aspect? Thanks.