Total of 12 dives and already a few lessons and one almost "near miss"

[SapphireMind]

1.4 has already a built in safety. I know that at least PADI mentions in case of emergency you could go to 1.6 temporarily ? Or maybe I don’t remember correctly

Like I said, I tend to the conservative, probably because I'm inexperienced. While that is built in safety for you, I prefer to not go to the edge of safety. As I get more comfortable, I will likely be more comfortable with all of the things, but my concern is always screwing something up (like going deeper than intended somehow) and hurting myself.

I have a very large goal in diving to not die.

 

[SapphireMind]

If you feel like you need extra safety you can use 1.2 or 1.3 instead of 1.4 ?

Yep, that's what I tend to do in my brain, 1.2. Again, it's theoretical for me at this point. I know they've done research and stuff, but I'm a wuss

 

[Schwob]

I've dove with many a "Divemaster" I would be scared to share a bathtub with.

...LOL...!!!

 

[BlueTrin]

I have a very large goal in diving to not die.

I don’t think you are a wuss, you explained your reasons and acted accordingly.

The problem with dying is that it may impair your progress as a diver, so kudos on your life goal too

 

[Manatee Diver]

Yep, that's what I tend to do in my brain, 1.2. Again, it's theoretical for me at this point. I know they've done research and stuff, but I'm a wuss

I wouldn't say you are a wuss just likely a victim of certification agencies greatly simplifying the nitrox curriculum.

O2 toxicity is like DCS, it is a function of exposure and time, and the NOAA publishes exposure limits for partial pressures as low of 0.60 PPO2. You have to dive 720 minutes to hit it, but it is still there. The exposure limit of nitrox at a PPO2 of 1.4 is 150 minutes per a dive, or 180 minutes total per day. Staying within no stop dive limits and only going up to the maximum nitrox available for recreational divers of EAN40, it is impossible to hit the single dive exposure limit and it would take at least 3 dives to hit your daily exposure limit.

But if you are diving nitrox you are likely diving with a computer, which means you can monitor your O2 exposure through it. Personally even on a day of aggressive diving on nitrox I rarely see my exposure higher than 25%.

 

[SapphireMind]

I wouldn't say you are a wuss just likely a victim of certification agencies greatly simplifying the nitrox curriculum.

O2 toxicity is like DCS, it is a function of exposure and time, and the NOAA publishes exposure limits for partial pressures as low of 0.60 PPO2. You have to dive 720 minutes to hit it, but it is still there. The exposure limit of nitrox at a PPO2 of 1.4 is 150 minutes per a dive, or 180 minutes total per day. Staying within no stop dive limits and only going up to the maximum nitrox available for recreational divers of EAN40, it is impossible to hit the single dive exposure limit and it would take at least 3 dives to hit your daily exposure limit.

But if you are diving nitrox you are likely diving with a computer, which means you can monitor your O2 exposure through it. Personally even on a day of aggressive diving on nitrox I rarely see my exposure higher than 25%.

Good to know. Like I said, it was a basic nitrox course - I did not expect to be an expert after it, just like I didn't expect to be an expert after my open water. I do have a computer, but it's fairly new and I'm still getting comfortable with using it and how to use it best.

 

[yle]

I wouldn't say you are a wuss just likely a victim of certification agencies greatly simplifying the nitrox curriculum.

O2 toxicity is like DCS, it is a function of exposure and time, and the NOAA publishes exposure limits for partial pressures as low of 0.60 PPO2. You have to dive 720 minutes to hit it, but it is still there. The exposure limit of nitrox at a PPO2 of 1.4 is 150 minutes per a dive, or 180 minutes total per day...
But if you are diving nitrox you are likely diving with a computer, which means you can monitor your O2 exposure through it. Personally even on a day of aggressive diving on nitrox I rarely see my exposure higher than 25%.

You're referring to pulmonary oxygen toxicity, and basic nitrox courses say little about this for exactly the reason you state: recreational divers will almost never attain an exposure high enough for pulmonary oxtox to be an issue.

CNS oxygen toxicity is different and is directly related to the ppO2... and therefore directly related to the diver's depth. This kind of oxygen toxicity is explained in greater detail (fundamental causes, how to recognize symptoms, etc) in basic nitrox courses because it is relevant to recreational divers.

 

[Manatee Diver]

You're referring to pulmonary oxygen toxicity, and basic nitrox courses say little about this for exactly the reason you state: recreational divers will almost never attain an exposure high enough for pulmonary oxtox to be an issue.

CNS oxygen toxicity is different and is directly related to the ppO2... and therefore directly related to the diver's depth. This kind of oxygen toxicity is explained in greater detail (fundamental causes, how to recognize symptoms, etc) in basic nitrox courses because it is relevant to recreational divers.

No those are the CNS numbers, the pulmonary toxicity requires an even greater amount of exposure measured over a period of days. At a PPO2 of 1.4 you have to dive in excess of 184 minutes a day (which note is higher than the CNS daily limit) for 15 days or more to exceed it. For shorter periods the daily exposure limit for pulmonary toxicity are even higher. Unless you are diving for a living or diving on a rebreather, pulmonary toxicity isn't remotely a concern for recreational open circuit divers.

 

[tmassey]

Maybe to clarify, because I am familiar with those calculations: I guess from my perspective, I like a wider margin of where I am safe. I tend to be very conservative

Be careful with that: changing one parameter to make things 'more conservative' does not necessarily make things 'more safe'.

When you're in the middle of a highway, walking slowly and carefully -- don't want to trip on those cracks! -- is *NOT* safer than moving as as quickly as reasonably possible across the road. Now certainly, there is a point where moving across the road faster is more unsafe (maybe slightly) than at a slower speed. But that doesn't mean that you should just *keep* going slower and slower -- after all, if a little slower is safer, than a *lot* slower has got to be a *lot* safer, right?

In crossing the road, there are multiple risks: passing cars and trip-and-fall hazards. You can't focus on one risk and ignore the other risk (or weigh one too heavily, etc.). You've got to balance them.

Same here. Diving Nitrox is balancing two risks: DCS/Narcosis (caused by the Nitrogen) and OxTox (caused by the Oxygen). Reducing one necessarily increases the risk in the other. You cannot simply say, "If X is safe, I'm going to make it MORE SAFE™ by increasing the buffer." You have to think about what you're stealing from to *get* your "MORE SAFE™". Eventually, the risk you're stealing from will make the total risk profile *greater* -- even though you're more protected from one of the risks, the other risks increase to more than offset that.

I'm not saying where that line should be for you. Backing away from even PPo2 of 1.4 may be a reasonable decision under a small set of specific circumstances. But remember: "a wider margin of where I am safe" from one risk (say, OxTox from PPo2 < 1.4) is also a 'narrower margin where I am at risk' (from DCS and narcosis from greater nitrogen). TNSTAAFL.

Stay safe -- but remember that always trying to be "MORE SAFE™" might actually be making you materially less.

 

[yle]

No those are the CNS numbers, the pulmonary toxicity requires an even greater amount of exposure measured over a period of days. At a PPO2 of 1.4 you have to dive in excess of 184 minutes a day (which note is higher than the CNS daily limit) for 15 days or more to exceed it. For shorter periods the daily exposure limit for pulmonary toxicity are even higher. Unless you are diving for a living or diving on a rebreather, pulmonary toxicity isn't remotely a concern for recreational open circuit divers.

Ok thanks... I always thought the risk of CNS oxtox was primarily associated with a high ppO2, i.e. something higher than 1.4 or 1.6, which varies with an individual and the specific conditions of the dive. I was led to believe that CNS oxtox could occur in the first few minutes of a dive, given the necessary conditions, so that "time of exposure" was a minor contributor at best. And I was led to believe this is why the MOD of the nitrox mix is an important parameter typically included on the label or logbook when nitrox is used.

But thank you for correcting me and setting the record straight.