Breathing below 300'

[halocline]

Since if I had said all regs are depth compensated someone else would have found a nit to pick so I used the word most, and still get accused of it. Have fun boys but this is getting tiresome.

Hey, don't feel bad. If you had said "all" regs and somebody told you it was wrong due to CCRs, I'm sure someone else would jumped in to your defense (I would have) and clarified "all open-circuit" regs, which I'm certain is what the OP was talking about. CCRs are a totally different animal. I freely admit I know basically nothing about them. I do like the cool mouthpieces, though!

 

[Navy]

I can't believe all of this went this far. Surface decompression tables using air only go to 190 feet.
I doubt if you could make it down to 300 ft with a regulator alive.

 

[Geoff_H]

I can't believe all of this went this far. Surface decompression tables using air only go to 190 feet.
I doubt if you could make it down to 300 ft with a regulator alive.

I know several guys who have successfully dived below 300ft and lived to tell the tale. They weren't breathing air though! When it's deep and dark you're on trimix (oxygen, nitrogen and helium) and you are doing staged decompression using different gasses on the way back up.

 

[Cave Diver]

I can't believe all of this went this far. Surface decompression tables using air only go to 190 feet.
I doubt if you could make it down to 300 ft with a regulator alive.

I'd venture that there are more than handful of people on the board that have been below 300', although none were on air. I can think of almost a half dozen that I personally know of.

I'm willing to bet there are a few that have done it on air as well.

Welcome to the board and enjoy your stay. There's a lot to be learned here.

 

[Gilldiver]

I can't believe all of this went this far. Surface decompression tables using air only go to 190 feet.
I doubt if you could make it down to 300 ft with a regulator alive.

My 1966 copy of "The New Science of Skin and SCUBA Diving" has the "US Navy Standard Air Decompression Table for Exceptional Exposures" going down to 300 feet.

The max dive given is 180 minutes at 300 feet.

Lets see, 20 minutes at 300 gets you 104 minutes of deco, add in the 20, plus travel time and you have about a 130 minute run time. That is if you remember anything below 250.'

 

[it_mike]

Not to nit-pick, but ALL regs are depth compensating for IP or they would not work.

Just to insure we have accurate data here, not ALL open circuit regulators are depth compensating.

Think balanced v. unbalanced first stages. My Mk2 is great for shallow, warm water diving, but I wouldn't take it much past 60' without a WOB hit, let alone past 100'.

 

[Fishpie]

it mike....you are confused.
A balanced first stage balances it against the tank pressure.
Your MK2 will breath fine at 100' as long as you have more than 700psi in your tank.
Those holes all around the end cap of your 1st stage allow the ambient water to excerpt force on the end of the piston to compensate for depth.

 

[halocline]

Just to insure we have accurate data here, not ALL open circuit regulators are depth compensating.

Think balanced v. unbalanced first stages. My Mk2 is great for shallow, warm water diving, but I wouldn't take it much past 60' without a WOB hit, let alone past 100'.

This is a common source of confusion. Balanced has nothing to do with depth compensating, although some reg manufacturers like to confuse the issue by calling their regs that supposedly increase IP more than increase in ambient "overbalanced." They should say "over-depth compensating" but that doesn't have the same pseudo-tech "I-don't-know-what-it-is-but-it-must-be-good" marketing appeal.

If regulators did not compensate for changes in depth, they would not work for diving.

And BTW, I've had my MK2 down to 130 ft numerous times and it works just fine. Maybe yours need a little tuning.

 

[DA Aquamaster]

I have also had Mk 2's to 130 ft. I also know technical divers who have had them below 200 feet on helium mixes, which on average flow about 20% more efficiently through any regulator.

A balanced first stage design, due to the nature and limits of the unbalanced piston design, will generally be able to have a larger orifice and a higher flow rate that will enable it to be used at greater depths than an unbalanced first stage - but all open circuit scuba first stages are depth compensated.

 

[Doppler]

I can't believe all of this went this far. Surface decompression tables using air only go to 190 feet.
I doubt if you could make it down to 300 ft with a regulator alive.

OH PLEASE! Like many other divers, I have logged several dives below 300 feet and regularly run advanced trimix programs to 100 metres (about 330 feet) using open-circuit gear.

My Mk2 is great for shallow, warm water diving, but I wouldn't take it much past 60' without a WOB hit, let alone past 100'.

I owned two old Mk2 / R190 combinations and have used them as decompression gas regs well below 30 metres (100 feet). There was NO work of breathing issues at all... NONE. I have regs serviced and set up specifically for the type of OC diving I do, but even in their basic format, those old ScubaPro first stages were bullet-proof. I still have them kicking around as backups and would not hesitate to dive them again.