Doing 'Light Deco' as a recreational diver

[*Floater*]

Lots of things are "common" but that doesn't make them smart. In fact, stupidity is pretty common.

A review of your OW text should bring back tidbits of wisdom like...to avoid decompression sickness, don't push the limits of your table or computer.

For best results, don't follow the idiots.

I don't see what's stupid about "light deco" as long as you know what you are doing.

To me staying 5 min or so over NDL (gas allowing) at a site that turned out to be unexpectedly fun and then spending extra time shallow to off-gas is smarter than cutting the dive short because of a somewhat arbitrary NDL time line.

 

[jeckyll]

Yeah, all my current mentors have been hammering on my team to get off our butts and take Tech 1 -- having more experienced divers tell you not to slow down but to speed up is a the better side of that equation to be erring on...

I don't know. Realistically on a Suunto with 5 minutes showing (2 mins mandatory + 3 mins safety stop) you're not in much danger at all. You can probably even go across that by another 5 mins at depth and while the Suunto will probably be telling you 10+ mins of deco to do, you'd be fine blowing it off if the absolute worst case happened to you.

The real question is if you're reserving enough rock bottom gas at that point to deal with a normal ascent plus 10 mins of deco for 2 divers, which comes to around an additional 400 psi for HP130s, or about 1400 psi at 100 fsw -- which gives you 2100 psi usable which is still good for a 30 minute dive at 100 fsw. Given that plan, given at least DIRF or Cavern level of skills, comfort doing OOAs and mask-off, etc and particularly if you're getting mentored by local technical divers then "Lite" decompression sounds not so bad.

If you're just blindly going over your decompression limits on your computer, mindlessly following what deco schedule it gives you and doing so on an Al80 with no idea how much gas you need -- well, that's an accident waiting to happen.

I left the bottom with 1500 psi in my AL 80 and a full slung 40. I exited with 800 after doing a 12 minute ascent. (as planned,still with a full slung 40). I don't really do much blindly and I had the highest gas usage on my team.

My thinking in starting this thread was really not so much about what I was doing, but more about what others were doing (specifically the ones carrying no extra gas). I don't know how much everyone had left, but I'm fairly sure one or two people were at 300 - 400 psi. (NOT the people I was diving with!).

That's scary stuff as far as I'm concerned...

As far as your posts go, while I hope you get better soon it's nice to see some well thought out responses

 

[lamont]

You're not still sick from MX are you?? Damn that would be some bad shrimp.

Yeah, I don't think that doing 4 dives and getting hammered on margaritas my last day there was the best setup for getting over this thing quickly. It lingered on as a headcold and now it has dropped into my chest and while it isn't bad and I'm at work today, it refuses to actually give up and go away...

 

[MikeFerrara]

I don't see what's stupid about "light deco" as long as you know what you are doing.

To me staying 5 min or so over NDL (gas allowing) at a site that turned out to be unexpectedly fun and then spending extra time shallow to off-gas is smarter than cutting the dive short because of a somewhat arbitrary NDL time line.

Nothing is wrong with decompression. In fact, if you go deep enough and stay long enough, I highly recommend it. Someplace, somehow between my couple of posts in this thread you misunderstood me to an extent that's barely imaginable.

The OP's question, as I understood it, dealt with recreational divers (I take it we can't assume they are well versed or necessarily equiped for staged decompression) just doing it anyway. This can be a problem for lots of reasons that have not only already been well stated in the thread but should be so obvious as to not even warrent much discussion.

 

[dsteding]

Yeah, I don't think that doing 4 dives and getting hammered on margaritas my last day there was the best setup for getting over this thing quickly. It lingered on as a headcold and now it has dropped into my chest and while it isn't bad and I'm at work today, it refuses to actually give up and go away...

That sucks. I hope you get better soon . . . we need you on team America.

 

[MikeFerrara]

I don't see what's stupid about "light deco" as long as you know what you are doing.

To me staying 5 min or so over NDL (gas allowing) at a site that turned out to be unexpectedly fun and then spending extra time shallow to off-gas is smarter than cutting the dive short because of a somewhat arbitrary NDL time line.

Nothing is wrong with decompression. In fact, if you go deep enough and stay long enough, I highly recommend it. Someplace, somehow between my couple of posts in this thread you misunderstood me to an extent that's barely imaginable.

The OP's question, as I understood it, dealt with recreational divers (I take it we can't assume they are well versed or necessarily equiped for staged decompression) just doing it anyway. This can be a problem for lots of reasons that have not only already been well stated in the thread but should be so obvious as to not even warrent much discussion.

 

[dumpsterDiver]

Realistically on a Suunto with 5 minutes showing (2 mins mandatory + 3 mins safety stop) you're not in much danger at all. You can probably even go across that by another 5 mins at depth and while the Suunto will probably be telling you 10+ mins of deco to do, you'd be fine blowing it off if the absolute worst case happened to you..

This is great information. So you can blow past the NDL at a recereational depth of say 130 feet and stay for 5 more minutes on the bottom and your computer will not give you more than 10 minutes of total deco time and you can probably blow it all off and be "fine".

Have you really done this? Do you really have experiece with diving in this manner? This "advice" is potentially very dangerous. I do 2-3 light deco dives per day and sometime a few more non-deco dives during a typical day while diving between 190 and 90 feet.

I can pretty much assure you that if you stay 5 minutes extra past the NDL limit at 130 feet on, say your third dive of the day, your computer will "spank you hard" and I would be very hesitant to blow off the deco. I have made this "discovery" the hard way. The situation is totally different (and you may be correct) if you stay an extra 5 minutes at 80 feet on the first dive of the day.


Your general statement could really get someone in trouble. I dive with a single computer and almost never look at tables. I follow my computer, do deep stops (that my old oceanic does not call for) and have a lot of faith in the deco information it gives. I have done so many similar dives however, that I pretty much know what my deco status is just by looking at my depth and gas supply. People can follow their computers, but they need to have the EXPERIENCE to know what the computer is going to tell them, "before the computer does".

 

[*Floater*]

Nothing is wrong with decompression. In fact, if you go deep enough and stay long enough, I highly recommend it. Someplace, somehow between my couple of posts in this thread you misunderstood me to an extent that's barely imaginable.

The OP's question, as I understood it, dealt with recreational divers (I take it we can't assume they are well versed or necessarily equiped for staged decompression) just doing it anyway. This can be a problem for lots of reasons that have not only already been well stated in the thread but should be so obvious as to not even warrent much discussion.

Okay, maybe I misunderstood you. I thought you were saying that the "light deco" (short deco on backgas probably without formal tech training) described by the OP was dumb. Personally I think it's fine as long as the divers understand what they are doing (increased risk, enough gas, etc.) especially since most computers are pretty conservative and may show mandatory deco when some other commonly accepted algorithms (like RGBM) would not.

 

[Meng_Tze]

I don't know how much everyone had left, but I'm fairly sure one or two people were at 300 - 400 psi. (NOT the people I was diving with!).

That's scary stuff as far as I'm concerned...

Isn't this somewhat the standard on most rec dives? The DM/Captain on a boat yells: "back on the boat in 45 minutes or 500 psi" The timing put out there is usualy the NDL (probably even that is adjusted)for that dive (depth/ depth-time).

So yes the majority of divers will follow the clock, run up to 45 mins, or run until they hit 700psi to start the ascend. Of course many will surface with 300 psi, or some will over run their computer and see Damocles's deco sword swinging.....

Its not so scary if you think about it, it is common practice and done every day. This is why NDL's have been set with such conservatism, to allow for people running behind and still be okay.

Of course as said before, based on personal criteria, you mileage may vary.

 

[rjack321]

Dumpster, Lamont was referring to the fact that Suunto has a particularly conservative algorithm and if the user was wearing say an Oceanic it might not be in deco at all. 5 mins on a Suunto probably = 5 mins left on NDL of some other brands.

Personally I don't use a computer for deco at all and I think Lamont and I would agree that 130ft really isn't a very recreational depth.