AOW check out dives...

[mikeguerrero]

Interesting, do you know if your instructor was using nitrox? When I had my Oceanic I found that it wasn't as conservative as the Suunto's. Granted id imagine hitting deco in an AOW class isnt something thats desired, since PADI is all about rec limits and no deco diving. How long were at 103fsw for?

Was the reg remove and replace done for your motor skills test to see if you were feeling the effects of narcosis? Again, id imagine that there better "puzzles" to solve at 103fsw to see if your narc'd than taking away your air supply and putting it back. Think of how bad it could have been if someone wasn't able to put it back.

Glad to hear that you made it back, and enjoyed your dives. Congratulations on getting your AOW cert! I may also have to agree and say that you might want to let PADI QA know about this. Had I been in your situation I would not have felt safe.

Brandon,

Our instructor dives Nitrox and during this dive yes he was on Nitrox. I have the Nitrox class but just haven't set up to take the test and do my dives.

We were at 103 feet and had a bottom time of 27 minutes. After we dropped to 103 feet our instructor lined us up and and we did the 5, 4, 3, 2, 1 and then reverse 1,2,3,4,5 with fingers; all of us passed that except for one diver that messed it up just a tad when he got to one he flipped off the instructor and then laughed.

Then all of us did the reg out blow out bubbles, that was super easy. He then asked if I wanted to pull off my mask and clear it, I told him NO....

After that we swam back to a rock and started looking at things when all of a sudden the computer went off in DECO.

I was really concerned because I know that when I dove deep with you, you were clear to keep us away from too deep, you said I don't want you guys going into DECO and you kept us clear, thanks Brandon.

Back to my dive I wrote on my slate, "why am I in DECO". He said, "it's okay just go up 10 feet and vent out gas, which is what I did and everything turned out okay.

I did a extra long 15 ft safety stop and never had any ill effects as I posted earlier, I've had worse days in shallower water.

I know I made a mistake allowing myself to go into DECO because I should have been watching my computer; making sure my bars didn't go to the large area that says you are now super close to DECO.

I have to learn to understand my computer and that's what I'm going to be pushing for in the next dives that I do. I don't know anything about it other than too fast ascent, psi, depth, temp... I need to really know everything...

Brandon does the Nitrox class really make the difference in diving? I've signed up for the class but really don't know anything yet other than it a higher mixture of O2 and your BT are longer at depth over just AIR.

What are the cautions to be aware with this gas if you could summarize it?

Thanks,

MG

 

[Hinalo]

I'd be interested to know what your dive profile was. You couldn't have been at 103fsw for the whole 27 minutes or your computer would probably have gone into deco mode sooner. You had enough air for a long safety stop, but do you remember how much air you had when your computer put you in deco?

 

[Gombessa]

I'd be interested to know what your dive profile was. You couldn't have been at 103fsw for the whole 27 minutes or your computer would probably have gone into deco mode sooner. You had enough air for a long safety stop, but do you remember how much air you had when your computer put you in deco?

That's exactly what I was thinking. 110ft throws you into deco at something like 15 minutes on any agency's table. That class, good or not, sounds like it was skirting the edge based on the profile given. I suspect in reality you guys were under 100ft for less than 10 minutes?

 

[bbianchi]

That explains why your instructor didnt hit Deco, the Nitrox was giving him a lower % of Nitrogen than you had exposure to.

Im guessing that you weren't at 103' for the full 27 min, otherwise you way exceeded Recreational limits. I was curious if you knew how long you were at the 103' mark for, just to compare you computer to what the tables say.

As far as you taking all the blame for hitting Deco, the instructor had you with his group of students, "under his care" if you will. Even if he was on Nitrox he should have been keeping an eye on the NDL limits for the students on air. Im just glad to hear that it sounds like the situation was handled properly on both your and his parts once you hit deco.

As far as the benefits of Nitrox, there are many. However the deeper you go you have to be more careful with it as well. As I learned in my Nitrox class you gain about 25% more bottom time on the first dive and nearly 50% on your repetitive dive. Plus if you do a live aboard or such it can decrease your SI requirements since there isnt as much Nitrogen to off gas and you can get more dives in that day. However, you have to watch your partial pressure saturation of Oxygen. The suggested limit is a partial pressure of 1.40, with 1.60 as the hard max. The risk if you exceed the limits is CNS Oxygen Toxicity. Basically Nitrox keeps you from getting as saturated with Nitrogen as you would for diving the same dive with Air. Like I said when going deeper you have to watch your partial pressures and keep them within limits. (Being that im on a teleconference as I type this it may not be the most complete/logical and I apologize)


For reference:

 

[mikeguerrero]

I'd be interested to know what your dive profile was. You couldn't have been at 103fsw for the whole 27 minutes or your computer would probably have gone into deco mode sooner. You had enough air for a long safety stop, but do you remember how much air you had when your computer put you in deco?

Jeff,

Remember I said Bottom Time 27 minutes not actual time at 103 feet. My understanding of SSI bottom time is the moment you start your ascent back to the surface; the whole time of the dive dropping down and then ascending.

Please correct me if I am wrong; my VT3 calls it actual time and elasped time, I took the actual time of the dive thats 27 minutes.

At 103 feet if memory serves me correctly it was about 10-12 minutes of time if that. I could give you the exact depth and time that the DECO commenced when I get home and take a look at the data; it's on my laptop.

SSI DOPPLER NO-DECOMPRESSION LIMITS BASED ON U.S. NAVY DIVE TABLES indicate that at 100 ft your limit is 20 minutes. Since I was at 103 I need to go to the next value, 110 ft limits you to 15 minutes.

Jeff thanks for the heads up...

MG

 

[Adobo]

Jeff,

Remember I said Bottom Time 27 minutes not actual time at 103 feet. My understanding of SSI bottom time is the moment you start your ascent back to the surface; the whole time of the dive dropping down and then ascending.

Please correct me if I am wrong; my VT3 calls it actual time and elasped time, I took the actual time of the dive thats 27 minutes.

At 103 feet if memory serves me correctly it was about 10-12 minutes of time if that. I could give you the exact depth and time that the DECO commenced when I get home and take a look at the data; it's on my laptop.

SSI DOPPLER NO-DECOMPRESSION LIMITS BASED ON U.S. NAVY DIVE TABLES indicate that at 100 ft your limit is 20 minutes. Since I was at 103 I need to go to the next value, 110 ft limits you to 15 minutes.

Jeff thanks for the heads up...

MG

Was there a dive plan? I am sure that it was known ahead of time that some (if not all) the students were diving air. It was also known ahead of time that ballbuster gets to 100+ ft. I am curious to know if these topics were covered as part of the class.

 

[Chuck Tribolet]

27 minutes on air at Ballbuster seems long. On Nitrox, I figure to be headed up between 31 and
35 minutes. And my typical profile spends about five minutes on the sand checking the gorgonians
for Simnia, and then up on the rock to 80-90.

Now about Nitrox.

I can't remember the last time I did a dive on air. When I dive with someone who's on air, I set
one of my dive computers for air, so I have a vague idea where they are.

On Nitrox 32, you PPN2 is (100-32)/(100-21) = 86% of your PPN2 on air, so you get (sorta)
100-86 = 14% more bottom time. You are limited to 132 feet or 111 feet depending on
whether your max PPO2 is 1.6 or 1.4.

On Nitrox 36, your PPN2 is (100-36)/(100-21) = 81% of your PPN2 on air, so you get (sorta)
100-81 = 19% more bottom time. Your max depth is 95 feet or 113', depending ....

I trained on Nitrox when max PPO2 was 1.6. I watched the lawyers dumb it down to 1.4. Will
I do the whole dive at 1.6? NO! But a short exposure to check the anchor and take a few
picture, no problem, IMHO.

Let's look at the cost. Assume an air fill is $5, a Nitrox fill is $10. I figure a day in Monterey costs
$50 for the drive (with the boat), $12 to park, $10 in boat gas, $20 in boat oil and maintenance,
and $10 for two air fills, so $102. So for another $10, I get 14-18% more bottom time. DO
THE MATH! And, more importantly, I get more diving.

Chuck

 

[dannobee]

One more thing, if you're working up the line, there's a chance that you were in deco, but you came up slow enough for your computer to clear.

This happens all the time with my Vytec.

It sounds like your computer did the same thing.

 

[DocWong]

Dude, about 103' for 27 minutes on air? You were in deco. I've learned the hard way to not dive at the limits of the tables. You can still get bent even if you go by the book so why push it. I think your instructor should have been more conservative with your profiles.

 

[mikeguerrero]

Yes there was a clear dive plan. We all knew that ball buster was 100 feet in fact just a tad deeper.

When we ascended we reached 100 feet and that's roughly where we did our skills. I some how explored just a tad more and reached 103.

When I saw my computer reaching 1500 that's when I started my ascent, that's what our instructor told us to do.

He stayed at the bottom and made each of us go up the line. Looking at my dive log:

Elasped Time / Depth /Tissue loading bar /Air pressure reading /ATR /DTR /DECO time
15 minutes /100 feet /8 segments / 1670 PSI / 17min /0 /4 min

Stop Depth 10feet/ Temp 53F/ Link Status Linked/ Dive status Decompression

According to my dive computer:

At 27 feet on my ascent is when I got out of DECO and got back the 7th bar segment. I had 1120 of PSI, 14 min of ATR, I did a 10 foot safety stop and ending with 1000 PSI...

MG

So in short: 15 minutes into my dive at 100 feet at ball buster with 1670 psi left in my tank I pushed my 7th bar segment to 8 bars and my VT3 said you are in DECO...

At 27 feet on my way back up I had given the 4 minutes of DECO time it wanted and it removed me from the 8th bar back to 7 bars and I could then do a safety stop and hit the surface...