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Hi @UWSojourner, thank you very much for the link. Now I still wondered why my calculation gave a smaller number and had a look at the last chart in your link: My calculation did not produce any supersaturation in the slowest compartment (#16, th=635min). In the NEDU dive with 30min @...

In the slides I wonder about the numbers of the ISS values: The unit of integral supersaturation should be "bar * min" or "mbar * min", but not "mbar/min". I guess this is a typo only, but assuming "mbar*min" as the unit, then the values shown here of about 1000 are very small. 1000...

AFAIK there's still no evidence that you can condition yourself against the effects of narcosis. But there's probably a correlation between nitrogen narcosis and CO2 buildup, and therefore it's not surprising that newish divers tend to suffer more than experienced (=more relaxed) divers. First...

I would not recommend teaching classes with i3, because students should know how to operate the standard inflator. I guess that's the reason why someone above wrote he saw instructors with both a standard inflator and i3 on their jackets. It's just we tried and found it easy with i3 to bring...

The i3 is a very good system. We used it in rescue classes and found it easier to use than the standard inflator. It's also no problem to reach with the right hand if necessary. It seems to me you have a strong opinion about things you don't understand.

Early CO poisoning symptoms usually include strong headache, dizziness, nausea... That's good because, unlike O2 or CO2, you have a good chance to notice the effects of CO early enough before it gets dangerous. But you must take the symptoms seriously and immediately tell your buddy, and call...

I don't see how a wing OP valve could ever freeze. There's no significant expansion of air happening in that valve, as opposed to first&second stages. Of course it can fail cause it's broken or full of dirt.

I wonder what that does to the durability of the o-rings in the reg. My LDS recommended me to o2-clean the interior of the reg and use o2-compatible grease only, but they don't replace the o-rings with Viton anymore because of quality issues. IIRC replacing the o-rings is not about fire (Viton...

Agree. @grantctobin seems to believe cold water SM is very different from warm water SM which I don't see. The main difference is in recreational diving, where a BM diver needs less space than a SM diver, so the operator will find it easier to cram a group of exclusively BM tourists onto his...

Do you use the necklace backup reg instead of unclipping/clipping the primary reg during switches?

I'm actually not sure if this is really necessary. The DIR backmount valve drill is special and you take a backmount class (Fundamentals, ITT, ...) to learn it. But then, let's say he takes Fundamentals and T1 or AN/DP in backmount, and then figures out that he can do dives with only 1 or 2...

"Coincidentally" the GUE chairman is the CEO of Halcyon, but that doesn't make Halcyon gear the only allowed option for GUE classes. Others vendors are fine. But there are requirements on the type of gear. Please contact your future instructor first before buying new gear, not to show up with a...

I don't know Sameh but I've been diving with Faisal and he's a good guy, can recommend. @YahiaAmed: Looking at your gear list it seems you dive sidemount. Note that GUE Fundamentals is a backmount-only class and cannot be done in sidemount gear. Taking the class won't hurt though, but it won't...

So the isolation valve was open while filling, but still got 1% difference. Did you open your isolation valve fully or just a little? Did you fill quickly from a storage tank or slowly from a compressor? If the valve is just a quarter turn open, it will equalize during the dive and allow for a...

This has been discussed a few times, e.g. Manifold failure - what should you do? that had examples of tank o-ring failures, or a guy who damaged his manifold while scootering in a cave and barely made it out. But these cases are very rare and there can still be a fallback; the buddy's long hose...

Yes VIP is not standardized by PADI. It just means if you're looking for a technical diving instructor teaching your kid 1:1 with a few extra days in DIR gear, you can get that with a PADI OWD card as well. But these VIP classes don't play a big role here anyway, too expensive. The more popular...

If you're concerned about this kind of valve failure underwater, consider that the isolation valve is a single point of failure for the issue you had. If the same defect your right post valve had occurs at the isolation valve then you lose all backgas quickly but can't do anything about it...

In Europe many shops offer a "VIP" option of the PADI OWD; don't they in the US? It's not a standardized offering by PADI, only the shops adding value. More days, and/or smaller classes. Of course it costs more, some almost double the price. A Tec diving shop near my place (a TecRec IDC) offers...

It's neither complacency nor lack of training, but human error. The one near-miss I witnessed was a GUE trained diver with GUE trained buddies. They certainly knew how the valve works and had done V drills before. Nobody could explain why it was closed during the dive, other than that he may...

Once again, I didn't say they should not recommend a manifold. The question is: why is the isolating valve inside the manifold still required if its safety track record is so bad? See this picture: File:Scuba Manifolds Schematic.png - Wikipedia The upper right one is the "non-isolation...