What's your PO2?

[Wookie]

BTW, 1.4 bottom with an allowable of 1.5 for seeing something REALLY cool but we aren't hanging around for long in that case. I don't do deco yet.

I might suggest that a limit of 1.4 "unless we see something REALLY cool" is not a dive plan, but is a good way to get hurt. So, what if there is something REALLY REALLY cool 10 feet deeper. and what if something is ULTRA cool 10 feet below that. Where does the coolness end and the dive planning begin?

Dive plans are not made to change on the fly. Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth. I was taught to cut a set of tables 10 feet deeper and 5 minutes longer than my actual dive plan. I think that's silly. I cut a set 10 feet shallower and 5 min shorter just in case I leave the bottom earlier than I planned, but I'm not going deeper or staying longer than I planned, because you can always come back later to see whatever is REALLY cool deeper.

 

[kanonfodr]

Wookie,

I'm not trying to slam you and your dive practices, but I consider the dive plan something that is resolved but malleable underwater if the team agrees to it. If we drop in and the current is heavier than predicted, or going the wrong way, or whatever then we adjust our plan to conform to conditions in the water.

But the key is having a skilled, disciplined team that can work and think together both above and below the water's surface. And if the team leader is doing something that one of the other members isn't comfortable with, we pull back and do something not so scary. Otherwise, he's the leader and while he is in charge, IMO the leader is also charged with making sure everyone has a good, enjoyable dive.

And if we see something really cool that's 10 feet deeper, then we can take a quick peek down there since we are planning our dive pretty conservatively on the surface, and keeping our brains engaged during the dive. So we may plan a PO2 of 1.2, and if we see something really cool 10 feet lower it's not a problem. And we have 2 or 3 more levels of Really Cool before it's an issue.

Peace,
Greg

I might suggest that a limit of 1.4 "unless we see something REALLY cool" is not a dive plan, but is a good way to get hurt. So, what if there is something REALLY REALLY cool 10 feet deeper. and what if something is ULTRA cool 10 feet below that. Where does the coolness end and the dive planning begin?

Dive plans are not made to change on the fly. Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth. I was taught to cut a set of tables 10 feet deeper and 5 minutes longer than my actual dive plan. I think that's silly. I cut a set 10 feet shallower and 5 min shorter just in case I leave the bottom earlier than I planned, but I'm not going deeper or staying longer than I planned, because you can always come back later to see whatever is REALLY cool deeper.

 

[peterbj7]

Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth

I don't agree with that. For any serious dive I always have a range of plans, and can switch between them for whatever reason. There will indeed be limits beyond which I won't go, probably, depending just what the implications of such a divergence might be.

For helium dives I'm much more strict with myself, because the effects of helium aren't well understood and I have no desire to get a helium bend under water.

 

[LiteHedded]

changing dive plans in the water is no big deal. stuff happens

 

[Wookie]

Well. I guess we've all found where we think someone elses decisions are decisions we wouldn't make ourselves. Ain't freedom grand?

And I don't feel slammed, I do things some don't agree with also. But to me, if you're going to change your plan on the fly, you'd better have discussed it on the surface, and, if you've discussed it on the surface, it's all part of the plan. Therefore, you haven't changed the plan, you've decided to use option 2 of the previously discussed plan.

 

[rjack321]

But to me, if you're going to change your plan on the fly, you'd better have discussed it on the surface, and, if you've discussed it on the surface, it's all part of the plan. Therefore, you haven't changed the plan, you've decided to use option 2 of the previously discussed plan.

By most people's concept we <barely> plan on the surface. Mostly rock bottom and maximum planned deco. Then again we're diving in the ~1.1-1.2 range on the bottom so there's tons of wiggle room on the MOD and its really not a limiting factor.

I haven't done a deco dive right up to a 1.4 MOD of my backgas ever. Recreationally I have stopped a few dives on EAN32 at 110ft. Partly that's a ppO2 issue, partly because that's where I draw the line on END. Most EAN32 dives don't even hit 100ft, the 110footers are unusual coincidences.

 

[LiteHedded]

I still haven't heard any reasons. the silence speaks pretty loudly

 

[muddiver]

Now, you tell me that 1.6 is an "Industry Standard" because someone published it in a book somewhere, my friend Ian had to get a certification card to do something he's been doing since before there were certification cards for it, and I'm making a stupid decision because I'm following the standards of the time I was trained. PADI issues C-Cards to divers diving voodoo gas without requiring them to make a dive using the gas.

I'm all for learning from mistakes. One of the problems with the industry is that folks make up "industry standards" with no basis for them. We've determined in this thread that some divers are more susceptible to ox-tox than others, some can tox at PO2's of 1.2 or less, and that some of us aren't as prone to suffering from ill effects of O2 than others. What are these industry standards supposed to do? Keep us safe? DIVING ISN'T SAFE, AND ANYONE WHO TELLS YOU IT IS IS BLOWING SMOKE UP YOUR ASS. Diving is a sport that carries some risk. It is up to each of us to define what level of risk we are willing to accept to accomplish our goals. When someone dies in the #3 pumproom of the Spiegel Grove, I don't say to myself "What an idiot!", I say "well, he tooks his chances and paid the price". I don't penetrate caves or wrecks because it's OUT OF MY COMFORT ZONE. I don't think that people who do are stupid, I just don't do it myself.

Humm...

The latest U.S.N. Diving Manual states in Chapter 10 Nitrogen-Oxygen Diving Operations, that dives with a PO2 beyond 1.4 are not permitted. It is also stated that CNS toxicity is usually not encountered unless the partial pressure of oxygen approaches or exceeds 1.6.

Yep, I'm pretty sure the Navy printed that up without doing any research.

 

[Jax]

Humm...

The latest U.S.N. Diving Manual states in Chapter 10 Nitrogen-Oxygen Diving Operations, that dives with a PO2 beyond 1.4 are not permitted. It is also stated that CNS toxicity is usually not encountered unless the partial pressure of oxygen approaches or exceeds 1.6.

Yep, I'm pretty sure the Navy printed that up without doing any research.

Is that the same Navy that used to say 1.6 and 2.0 was okay? (So sayeth a Navy Captain.)

 

[muddiver]

Is that the same Navy that used to say 1.6 and 2.0 was okay? (So sayeth a Navy Captain.)

Diving physiology is linked to medicine and our veague understanding of human physiology. Someone once made a wise statement that medicine is not an exact science. Therefore, diving physiology, on which decompression theory and the effects of breathing gases on the human body are based, is probably also not an exact science so there will be changes occationally based on our experiences with the occurances of OxTox, Nitrogen Narcosis, HPNS, etc.

The U.S.N. Diving Manual has not been updated since 2005 so with revision 6 I would think there would be some changes. Funny how they fit the standards of some of the recreational diving training agencies.