"Riding your Computer Up" vs. "Lite Deco"

[tbone1004]

I believe we need to look a fundamental difference in the dive profile. Does the diver plan on exceeding the NDL and incur a specific amount of deco. As such, does the diver account for the gas required and what happens when SHTF. If it's a planned deco dive, I don't see any problems. Although, you should obtain the necessary training. While the internet has loads of information, you may have overlooked something. There is no substitute for training and actual experience. On the other hand, we may have a scenario where the diver unwillingly enters deco. IMHO, scenario one is okay. Scenario two is just asking for trouble.

so this is removing my instructor hat.
Recreational divers have already been trained to make decompression stops in the form of safety stops. 3-5 minutes and it was optional. For a true recreational diver, changing the optional to mandatory seems to be what you are discussing. So, there are a couple ways to look at this.
Diving square profile tables, you are diving a VERY high gradient factor equivalent, at least by my standards *roughly a GF Hi of 95 if we are comparing to ZHL-16C*, and this corresponds pretty close to PADI's RDP for NDL's. We'll stay within the bounds of Shearwaters Rec. Nitrox Mode since we have a recreational hat on. Being a well read diver, you realize that this may not be the best gradient factor to be using for you because of a myriad of reasons and you have read up on gradient factors that others use and found the medium setting with a GF Hi of 85 to be pretty close to the profile that GUE et al use, and the high setting at 75 to be pretty close to many technical divers. You decide that to add safety to your dive profile you are going to use the medium or high setting for conservatism but that now means that you are going to violate the NDL's. You have done proper dive planning using available tools and have come to the conclusion that *I don't have the numbers here, so play along* that if I go to 100ft for 20 minutes on Low, then I'm in NDL's, but if I go to 100ft for 20 mins on High then I have a mandatory 7 minute decompression stop. I know that if I was diving on Low that my dive is within NDL, and per PADI I have a mandatory 3 minute safety stop. With my current safety factor, I have a 7 minute decompression stop at the same depth, but the dive plan was the same.
That is well within "lite deco" limits for me because you are only going into decompression because of your chosen safety margins as opposed to blindly following tables. I don't think you need a certification for that kind of diving personally, just be well read, and have your act together.

TLDR: If your dive is within the limits of the PADI RDP or a software program with a GF Hi of 90 or higher, and you choose a more conservative GF which puts you into deco while following the same depth/time profile, then I don't believe you need a decompression cert. Your deco time is unlikely to exceed 15 minutes, and if you were diving more aggressive conservatism settings, you'd be within ndl. This is obviously my personal belief and not that of the agency that I belong to.

 

[RyanT]

I don't think you need a certification for that kind of diving personally, just be well read, and have your act together.

I pretty much agree with everything in t-bone's post. I would to reiterate the "well read and act together" part. As I discussed with my previous experience of being surprised with an unexpected 30 min hang, the planning is important. I was just lucky that I happened to have the gas to finish the deco. Fortunately, we now have planning software and computers that make this easier. Aside from the planning software, computers, like my perdix, now give you your "time to ascend" in real time. Back in the day, when my Orca EDGE went into deco, it just said you were in deco. You didn't know until you got shallower how much hang time you had. So things are much better now, but learning how to take advantage of planning tools and knowing what to expect is really important.

 

[halocline]

It's certainly true that the line between aggressive NDL diving and a small shallow deco obligation is fuzzy. So an individual diver could do a fairly aggressive dive wearing 2 computers; one would tell him he's doing an NDL dive, the other would say he has a "lite" deco obligation.

It's also true that the risk of injury increases as one dives more aggressively. Technical training and equipment mitigate the increased risk of deeper, longer dives, and I think it's important to note that most of the people posting that they're comfortable with small deco obligations on otherwise recreational dives are also experienced and trained decompression divers. There's a big difference between that and a relatively inexperienced diver simply staying down longer and then having to pay for it with a stop. I guess a more useful distinction than "lite" deco would be "unexpected" deco.

I tend to treat longer deeper recreational dives that I do as "lite" deco dives by extending my stops, 3 mins at 20 ft and 5 or more at 10 ft. I'm not so concerned about DCS, it just makes me feel much better after the dive.

 

[Scuba J7]

Umm not sure how to address this...I'll just stop.

Cheers

I never flatter myself. I see that as a major flaw in an individual. So, you claim to be a "Dive Industry Professional". What is that, exactly?

That pic was just Andy being Andy. Made me laugh too, that jerk. I read the text in front of the pic, good stuff in there.

Sure sounded like it from your "Information" and avatar...

It flatters you, go with it.

Ambiguous.

"I do work as an employee for a SP dealer"
or is it
"I also do work for a SP dealer"

That says a lot.

 

[scubadada]

Exactly, I'm just fishing for rough numbers and fuzzy reasoning.

-Just for my own curiosity as to where I stand with respect to other opinions.

Thanks.

I do light deco on about 5% of my dives. My average deco time is about 5 minutes, the range is 2-14 minutes. I generally extend the last stop several minutes, 3-5.

 

[redacted]

I dive an Oceanic Data Plus which has a liberal algorithm. But I use its tissue loading bar graph to add a level of conservatism by normally limiting lead tissue compartment loading to about 85%. And I rarely pass anyone during the ascent.

 

[lowviz]

...I'll just stop.

Cheers

Me, too. Cheers.

-chalk it up to years of being totally ignored by SP: phone, letters, email. it finally comes at a cost. I still buy some of their gear, but hate myself for it.

My apologies if I was unfair to you.

 

[lowviz]

...//... I tend to treat longer deeper recreational dives that I do as "lite" deco dives by extending my stops, 3 mins at 20 ft and 5 or more at 10 ft. I'm not so concerned about DCS, it just makes me feel much better after the dive.

That is an interesting choice of stops, very effective for off-gassing.

Most recreational dives use either 15' or 20'.

May I ask what thinking/instruction you are following?

 

[halocline]

That is an interesting choice of stops, very effective for off-gassing.

Most recreational dives use either 15' or 20'.

May I ask what thinking/instruction you are following?

Sure, it somewhat mimics what is typically required when entering deco. I also think the recommendation for a 15 ft safety stop is a bit of a compromise; it allows for some inability to hold a stop accurately, and is probably less likely to result in new divers surfacing inadvertently. As far as the 20 ft stop, it might help with some of the slower compartments that could be a little stressed at 10 ft. I don't really know, and my computer doesn't indicate compartment loading. (maybe I should have bought a perdix, but I got such a good deal on my liquivision I couldn't say no) Anyhow, what's the rush?

 

[Basking Ridge Diver]

That is an interesting choice of stops, very effective for off-gassing.

Most recreational dives use either 15' or 20'.

May I ask what thinking/instruction you are following?

In line with this "methodology"...
Ascending from a scuba dive, | deep stops, |ascent rates, |safety stops, | time limits, | and gas needed