Exceeding Regulator depth rating

[Rhone Man]

I took a Sherwood Brut to 185 feet once. It was like breathing glue, but I got air out. If/when I ever go back, I'll try and use a higher performance reg.

 

[martzak]

That is something. NAUI used to give you air tables that went to 240 feet. And now they are pushing helium for 140?

From Wiki:
Divers breathing air at depths greater than 60 metres (200 feet) face a risk of an oxygen toxicity "hit" (seizure). Divers using a gas mixture enriched with oxygen (nitrox) who descend below the maximum depth allowed for the mixture can similarly suffer a CNS seizure at lesser depths.[19]

I've been down to 165ft on air...not that I want to make a habit out of it or anything.
180ft on air (TDI extended range diver depth limit) may be too close for my comfort (especially for repetitive dives) and I certainly am not about to dish out close to a $100/refill for helium-mixes. So will have to do some research on this.

Anyone with extensive experience diving to such depths on air, please feel free to chime in.

 

[beanojones]

I've been down to 165ft on air...not that I want to make a habit out of it or anything.
180ft on air (TDI extended range diver depth limit) may be too close for my comfort (especially for repetitive dives) and I certainly am not about to dish out close to a $100/refill for helium-mixes. So will have to do some research on this.

That's what it used to be like. In training, Air to 180 feet or so.

I understand the idea behind pushing helium for lower depths: Students who are more likely to be task loaded during dives, need the mental 'sharpness' trimix offers over air at even moderate tech depths (Taking moderate here to be 140-180 feet.)

But as you have noted, Trimix is insanely expensive. Personally for any dive to CNS limits of air (200 feet), I would never consider Trimix. As expensive as it feels for you on the mainland, it is absolutely insane out in the Pacific. Full Trimix courses are over $3000.00, mostly for the fills. A fill for a set of doubles is $400 +. A 200 foot dive on air only requires an O2 fill for deco, and gets you out of the water in about an hour. But without the experience to handle the narcosis, it's not a good idea, maybe. And any personal decision I make about diving comes with the fact that at any spot I would be diving deep at, I have at least a couple of hundred dives experience at that site. That essentially eliminates any task loading from handling the navigation for me.

So trimix is an entirely reasonable option, for some, and maybe especially so for training. It lets you do specific dives that you either simply cannot do on air, or you could do, but have no memory of afterwards because of narcosis. And along the topic of the thread, it makes regulator performance much less of an issue, because the density of the gas you are breathing is so much lower.

But you should have no problems with any modern regulator. (For the purposes of this discussion, a Sherwood Brut is not a modern regulator.) You may make decisions that will leave you options open for the future tech diving, like not using an unbalanced piston design except for deco bottles. But other than that one specific thing, any reg that you feel comfortable using will do.

 

[ba_hiker]

ItÃÔ a liability issue they have to pick a number, I think it is done out of a hat I have had ancient regs below 300ft, they were well care for though.

The number may be out-of-the-hat as you describe, but there are technical specs that must be met at the selected depth, in order to qualify for the CE cert. I believe the spec is something like -- the regulator must be able to support two panicked divers inhaling at the same time AND depressing there BC inflators at the same time and still diver a good breath to both. This is why current higher performance regulators have such high air delivery rates.

In addition there are other standards that must be met.

 

[beanojones]

I believe the spec is something like -- the regulator must be able to support two panicked divers inhaling at the same time AND depressing there BC inflators at the same.

(Which actually sounds like a reasonable approximation of an out of air event while narc'd out of your skull.)