How deep can you theoretically go on single tank?

Spoon · Jun 22, 2005

all the limits aside, how deep can you go on a single cylinder? was just wondering cause i keep hearing about recreational limits etc. etc. but see divers all the time go well beyond em and still have enough air to do their deco stops. just wondering if you guys really follow the 60ft max limit for OW, and 130ft limit for recreational diving?. i wasnt trying to be reckless, careless or stupid or anything but i may have been a bit naughty in my last couple of dives :crafty:

ScubaFreak · Jun 22, 2005

Well unfortunatley, there's no real exact answer to this, as it will be different for every single person. Lets try breaking it down a little.

The deeper you go the more air you use. The more experienced you are, the less air you use. If You and I were to go to 35metres for 10 mins, there would probably be a significant difference in the amount of air we use.
Technically, going to about 66metres, air becomes toxic as your 02 limit is reached, but again, this has been disproven by various divers going even deeper on air.

At the end of the day, lots of the explanations boil down to peoples shape, size, and physical makeup.

If we know our breathing rate, we can work out how long a tank will last us at certain depths, so that can be kinda cool!

Hope this helps a little

Dave

paolov · Jun 22, 2005

Spoon:
just wondering if you guys really follow the 60ft max limit for OW, and 130ft limit for recreational diving?.

the key word is RECOMMENDED depth of 60ft and 130ft. respectively for safety reasons.

how long a diver can stay under depends on the efficiency of breathing at depth considering the divers SAC rate.

TeddyDiver · Jun 22, 2005

Spoon:
all the limits aside, how deep can you go on a single cylinder? was just wondering cause i keep hearing about recreational limits etc. etc. but see divers all the time go well beyond em and still have enough air to do their deco stops. just wondering if you guys really follow the 60ft max limit for OW, and 130ft limit for recreational diving?. i wasnt trying to be reckless, careless or stupid or anything but i may have been a bit naughty in my last couple of dives

Staying at 50m(166') 5min bottom time Descendin/Ascending whithout delays (10m/min) on the way there's no deco.
Air needed (metric) with 30ltr/min use you use about 1800ltr which is a bit less than alu80 capacity (2000ltr). To be safe you need 1/3 spare air left so tank needed is 120 (15ltr botle,3000ltr capacity) Hope I did calculation about right in my head, and not quite sure about those cf's...

Diver0001 · Jun 22, 2005

Spoon:
all the limits aside, how deep can you go on a single cylinder? was just wondering cause i keep hearing about recreational limits etc. etc. but see divers all the time go well beyond em and still have enough air to do their deco stops. just wondering if you guys really follow the 60ft max limit for OW, and 130ft limit for recreational diving?. i wasnt trying to be reckless, careless or stupid or anything but i may have been a bit naughty in my last couple of dives

The theoretical answer to this is that the regulator needs an internal overpressure of about 10 bar to function. So strictly theoretically you should be able to take a scuba tank to about 190ATA (about 2km) without it imploding. After one breath it would probably implode, though.

In practice 100 metre dives on open circuit are common using 4 or 5 tanks. The deepest dive ever was something like 318 metres but that many more tanks than you can actually carry (I think it was 26 or something).

Off the top of my head any dive deeper than 50 metres becomes a decompression dive within a minute or so. While you can get that deep and back again on a single cylinder I would question the wisdom of doing so. In the 80's some people I knew were doing 60 meter bounce dives on single cylinders but these dives really are bounce dives. In terms of ability to make a non-bounce dive within the NDL's 40 metres is about the limit.

R..

MikeFerrara · Jun 22, 2005

The issue isn't the number of tanks, it's volume and redundancy. You need enough gas for the dive plan and contingencies and at some point you'll want redundancy. IMO, the 80 cu ft tanks that are so popular don't have any place much below 100 ft except as decompression or stage bottles.

The biggest concern with deeper dives is training and experience. Divers blow away recreational diving recommended limits all the time but they know how to clculate the needed gas supply.As you get more training those recommended limits change. For example, the recommended mas depth for some one with a TDI advanced trimix certification is 330 ft. BTW, divers don't stay within that either.

pieohpah · Jun 22, 2005

As counted in the nitrox certification class, the absolute operational depth with regular air is aproximatly 66 m (around 200ft) i.e. partial pressure of the oxygene reaches 1,6 causing a poisoning effect. So if diving deeper than that you definitly have to breath something else. Not mentioning getting drunk on nitrogene much before that.

Just a thought! =)

pieohpah · Jun 22, 2005

pieohpah:
As counted in the nitrox certification class, the absolute operational depth with regular air is aproximatly 66 m (around 200ft) i.e. partial pressure of the oxygene reaches 1,6 causing a poisoning effect. So if diving deeper than that you definitly have to breath something else. Not mentioning getting drunk on nitrogene much before that.

Just a thought! =)

...and I know; you should calculate with partial preassure of 1,4 for maximum operational depth. i.e. 55 m (~165 ft)

miketsp · Jun 22, 2005

ScubaFreak:
..snip..
Technically, going to about 66metres, air becomes toxic as your 02 limit is reached, but again, this has been disproven by various divers going even deeper on air.
..snip..

I don't think this is exactly what you meant to say and some people may get the wrong impression.
Once you go beyond 1.4PPO2 you are playing with statistics which get worse the longer you stay there.
Sure I know divers that have bounced to 85m without taking an O2 hit. Doesn't mean it's been disproven.

Kim · Jun 22, 2005

pieohpah:
As counted in the nitrox certification class, the absolute operational depth with regular air is aproximatly 66 m (around 200ft) i.e. partial pressure of the oxygene reaches 1,6 causing a poisoning effect. So if diving deeper than that you definitly have to breath something else. Not mentioning getting drunk on nitrogene much before that.

Just a thought! =)

Actually some people have been beyond the ppo2 1.6 limit - well beyond. Sheck Exley did a dive to 465ft on air - of course it wasn't with a single tank! :eyebrow:

Of course it's not something to try and copy!

How deep can you theoretically go on single tank?

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