Scuba Snopes

[RJP]

Adiabatic heating only occurs in steel tanks.

And doesn't (or shouldn't) occur when transfilling tanks.

 

[Abdullah]

Diving with a long knife strapped to your leg is cool.

Depends where it's strapped

I might have to go with Chatterton on the big knife discussion - a long blade has a lot more uses than a short blade. But, that's a different thread...

 

[Mr Carcharodon]

CLAIM: A diver swimming in a waterway gets too close to a grate and then gets sucked into the intake pump of a nuclear reactor and only survived because he got diverted into a holding pond instead of the main pump.

FACT! It was the Port St. Lucie Power Plant in S. Florida. I did a refueling of that power plant a few months after the incident. Everyone was still talking about it, and it was listed in the accident/incident log.

My local power plant does have a grate, and does have a holding tank where the fish that get sucked up go to (at least the lucky ones). And yes I made a dive out there years ago when there was no smoke goings up the stack.

 

[ianr33]

Breathing trimix makes you feel colder.

 

[kaerius]

Steel HP tanks don't get lighter when they get empty, only AL80s do.

A missunderstanding with a grain of truth. Steel tanks don't get positively buoyant when empty. The weight difference between full and empty for the same amount of gas is of course the same, but aluminum tanks go positively buoyant when empty and steel tanks don't. IE: AL80 goes from about 4kg neg, to 2kg pos, and LP80 goes from about 8kg neg to 2kg neg, HP80 would have even greater weight, and larger difference between empty/full(due to higher maximum pressure).

 

[Kevrumbo]

You can use Air Tables to dive Helium mixes recreationally within no decompression limits. . .
-----
Not recommended!

Shallow depth NDL's on Helium can be less than Nitrox, or even Air diving:

From Bruce Wienke, Technical Diving in Depth, Reduced Gradient Bubble Model (RGBM) In Depth: Helium NDLs are actually shorter than nitrogen for shallow exposures . . . Reasons for this stem from kinetic versus solubility properties of helium and nitrogen, and go away as exposures extend beyond 150 fsw, and times extend beyond 40 min or so.
Helium ingasses and outgasses 2.7 times faster than nitrogen, but nitrogen is 1.5 to 3.3 times more soluble in body aqueous and lipid tissue than helium. For short exposures (bounce and shallow), the faster diffusion rate of helium is more important in gas buildup than solubility, and shorter NDLs than nitrogen result. For long bottom times (deco and extended range), the lesser solubility of helium is a dominant factor in gas buildup, and helium outperforms nitrogen for staging. Thus, deep implies helium bottom and stage gas. Said another way, transient diving favors nitrogen while steady state diving favors helium as a breathing gas.

Helium offgassing

The greater diffusivity of Helium from a free phase bubble model perspective (i.e. RGBM) means possibly loading idiopathic bubble seeds/bubble nuclei and having a Boyle expansion pathology resulting in DCS upon ascent --even if you were diving trimix within air or nitrox NDL's. . .

Recreational Trimix

The best Rule-of-Thumb for diving Trimix IMHO/IME is to always at least use Oxygen as the last deco gas before surfacing --even for trimix single tank repetitive diving within recreational NDL air limits-- at least do an O2 "safety stop" on the last repetitive Trimix dive of the series. . .

 

[BDSC]

I've seen this a number of time on SB,

"I can watch someone during a dive or watch them set up their equipment and can tell you what agency he was certified under."

 

[PfcAJ]

A missunderstanding with a grain of truth. Steel tanks don't get positively buoyant when empty. The weight difference between full and empty for the same amount of gas is of course the same, but aluminum tanks go positively buoyant when empty and steel tanks don't. IE: AL80 goes from about 4kg neg, to 2kg pos, and LP80 goes from about 8kg neg to 2kg neg, HP80 would have even greater weight, and larger difference between empty/full(due to higher maximum pressure).

Some steels get positive. All tanks are lighter when empty then when full. Gas has mass!

 

[Pullmyfinger]

I've seen this a number of time on SB,

"I can watch someone during a dive or watch them set up their equipment and can tell you what agency he was certified under."

I might be able to tell you who they didn't get a certification with.

 

[TheDeuce]

What the heck, I'll weigh in:

You can dive Nitrox to increase safety OR increase bottom time. Not both.

MYTH BUSTED!



(Of course, around here it's often parsed to "you can dive Nitrox to increase safety")





m.