deco myths

[Lorenzoid]

GUE uses the term "minimum deco" to refer to what some refer to as "no deco."

 

[beldridg]

NB: I haven't watched the video but I'm pretty sure I can interpret the content.

I think that one thing to keep in mind is that there is no black-and-white division between "no-deco" and "mandatory deco" dives -- especially in the world of dive computers and multi-level diving.

For example, I think the default Shearwater recreational mode gradient factor is 40/85? I generally run 50/80 which will change my NDL on the same exact profile as somebody running the default. Other computers with proprietary algorithms have different conservative factor settings. The "no-deco" limit will be determined by those settings.

The one thing I learned a long time ago (I think from J. Chatterton) is that "nobody ever got bent from doing too much decompression time" which can also be IMHO expanded to "safety stop time."

When I was in Bikini recently I would add at least 3-5 minutes on top of the 45-60 minute deco time. I would generally run my SurfGF down below 70. Same thing with my recent expedition to visit the USS Moray.

My advice to all divers is that there is no glory in surfacing early and extra time on deco or safety stops certainly won't hurt (assuming you have the gas to do so).

- brett

 

[Cthippo]

When I was in Bikini recently I would add at least 3-5 minutes on top of the 45-60 minute deco time. I would generally run my SurfGF down below 70. Same thing with my recent expedition to visit the USS Moray.

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!

 

[inquis]

He also uses the phrase "deco dive" to mean one with a mandatory decompression stop, in contrast to a "no-stop" dive.

That's not what I got out of the video. [...] In contrast to a "deco dive" which has mandatory decompression stops.

Are we not saying the same thing?

 

[Member002]

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!

It's pretty zen. I just relax and zone out a bit. Occasionally while drifting you'll see some neat terrain or animal life, but usually it's mostly just blue nothing. When you're on a mooring line you can people watch a bit as recreational divers go up and down, and you'll see wildlife usually.

Ultimately, no, it's not much fun. But we're all adults capable of being bored for an hour. The idea is that it's "worth it" to do deeper/longer dives.

Would rather make a couple of shorter dives

Eventually, when you want to start going far into overheads, or hitting wrecks at certain depths, you don't really have the option of multiple shorter dives. For me that the general reason I'll do long deco. I'm happy to do multiple dives with light deco if I'm checking out a shallow wreck or not going to far into it, but sometimes when you want to see specific areas far inside deep wrecks, you just can't safely do it without a lot of deco.

 

[Member002]

The "Every dive is a deco dive" argument is always weird to me. Everyone always fundamentally agrees on everything yet argues about random pedantic stuff.

There are interesting things to talk about with this topic. How NDL vs deco gets taught, how playing with GF can change an NDL dive to a deco dive. Like go have a conversation with a recreational diver who sets their computer to 90/90 and does "ndl dives" riding the line and ask if there isn't something worth thinking about with regard to how we teach "ndl" diving.

 

[Blackcrusader]

I understand there are limitations in recreational diving that tech divers are not subject to

That would be depth then? Use of CCR? Planned Deco ( some of the divers here may do an unplanned deco dive if they have sufficient gas for a single tank ) dives at depths shallower than 40m depth are also recreational dives.

 

[Blackcrusader]

I'm not ashamed to admit I have no clue what setting a computer to 90/90 actually means.

There is no shame in not knowing. A friend of mine who has TDI ANDP and Padi instructor bought a Perdix after diving with me. I have had to show him some settings and get him to read about GF functions and settings.

Well my low is GF45 ( for deco dives ) and GF 95 for NDL dives. If you have a DSAT table take that as 100%
GF95 is then 5% more conservative than the table. GF85 is 15% more conservative so your NDL time at depth is less.
It is a way for default settings to be conservative so divers are not pushing the limits on NDL dives.

For Deco dives that requires other training.

 

[Blackcrusader]

I dive an older Oceanic. There are settings for PO2 limits, and alarms for whatever range of N absorption you may care to specify, but no GF functions.

Yup my dive buddy had two. They both played up on our dives in Bali last year. We've been diving together for several years now and also on night dives he really likes how easy the Perdix is to see. So we make sure we have the same settings on our dives together. Sometimes our guides need to stay shallower as they often use Sunnto with quite conservative settings.

 

[EFX]

Mark Powell states that all dives are decompression dives in that the tissues offgass or decompress on ascent. My wife who is not a diver understands this concept. After a late night dinner of pepperoni pizza with extra cheese when we're in bed she complains. I tell her, "Honey, relax. I'm just offgassing. You don't want me to get bent do you?"