The depth shall be 60, 60 shall the depth be, 61 is right out unless your AOW certified????

[NAM001]

I always understood it as:
OW : 20m CESA available and high NDL (longer than most divers gas supply)
AOW: 30m no CESA, beginnings of narcosis issues, NDL more often the limiting factor.
Deep: 40m, END now an issue, some agencies go helitrox here.
Tec 40/ Tec1: Intro to deco, usually on backgas so few stage bottle requirements. First twinset for most.
Tec 50: To make money, adds stage bottles in some agencies, gas switching protocols?
60 m course ( Naming gets very weird per agency): Limit for normoxic. Almost all agencies are on trimix by now.
100m course: Hypoxic trimix

Too bad more dont see it this way.

 

[TMHeimer]

I always wonder if DMs on charters are Deep Certified if guiding divers below 130'. I know there is a new (well 2010) Deep component to the DM course, but am not sure if it is the same as having Deep Cert. to 103'.

Too bad more dont see it this way.

20m (66') for a CESA-- I know it's been done from deeper, but wouldn't want to try a 20m CESA. Don't forget when you learn it in OW you start with a full breath, which you may not have (if you could get a full breath you'd at least start off with a normal ascent).

 

[dmaziuk]

... when you learn it in OW you start with a full breath, which you may not have (if you could get a full breath you'd at least start off with a normal ascent).

My OW instructor's follow-up was but you will be highly motivated to get there.

As I recall there's about 2 litres of stored oxygen in the body and only some (30%?) is in the lungs -- that's after breathing uncompressed air. ISTR it should be enough to keep you going for a minute. ICBW, mis-remembering, and all that, of course. One should be able to cover more than 20 m in a minute, even in gear with all of its drag. I would not want to try that either, but 40 m should be doable though extremely unpleasant. With a high risk of DCS unless it's the very first dive of the trip and you splashed with an empty tank.

 

[boulderjohn]

Do not forget that the tank is not empty--the regulator cannot deliver air at the depth at which you feel you are going OOA. As you get shallower, more air will be available if you inhale.

 

[Gareth J]

I think DAN says something along the lines of you are covered to any depth as long as it is within the limitations of your qualification. UNLESS you are involved in a rescue where they do not apply a limit.

It is true that very old diving qualification may not have a depth limit, or one that is considerably deeper than the CURRENT version of the qualification.
When I qualified at the start of the 90's PADI certainly had a depth limit around the 20m point (no stop diving only).

The BSAC had a maximum depth of 50m, which I think was valid for third, second and first class divers. Later the BSAC qualifications changed to Novice (diver under training), Sports Diver, Dive leader, Advanced diver and First Class. I believe 50m was the maximum for sports divers and above. They then moved the limit to 35m for Sports divers, 50m for dive leader and above. Qualifications and guidelines have changed over the years but this is still the position. HOWEVER the BSAC would strongly prefer divers not to use air below 40, and switch to Trimix for deeper dives.

Even my TDI card is effected by this moving of the depth limits. My Trimix card is depth unlimited, gas mix unspecified.
Since my qualification was gained, newer course have been added, and there are now progressive limits on depth and gas mixes dependent on qualification.

Part of the change relates to the number of people diving, commercial pressures, concern over litigation, and improved understanding of the effects of depth. When I started, air was the diving gas. Access to other mixes was only available through the scientific diving community or the commercial sector. Since then, Nitrox has appeared (the dveil gas ) which is now accepted as safe, and Trimix. Once you where considered a serious risk taker if you used Trimix, now you are considered foolish to dive air below 40m rather than the 'preferred gas' of Trimix.

Gareth

 

[Killerflyingbugs]

20m (66') for a CESA-- I know it's been done from deeper, but wouldn't want to try a 20m CESA. Don't forget when you learn it in OW you start with a full breath, which you may not have (if you could get a full breath you'd at least start off with a normal ascent).

I had to do 66' CESAs in dive school, just slowly blow out and don't freak out a lot of it is in your head, the calmer you are the longer the O2 in your body lasts. You can do them from way deeper, even if you have a deco obligation they can usually fix bent easier than dead.

 

[Steelyeyes]

My understanding is you are qualified to dive the deepest an instructor taken the you. My AOW was to 140' on a wreck (actually two wrecks laying next to each other, one wreck from WWI and the other from WWII) but my instructor put down 130' in my log book so he wouldn't get in any trouble ;-)

Guam?

 

[NAM001]

I had to do 66' CESAs in dive school, just slowly blow out and don't freak outa lot of it is in your head, the calmer you are the longer the O2 in your body lasts. You can do them from way deeper, even if you have a deco obligation they can usually fix bent easier than dead.

Yes sub school does the same thing but the reality is that most that have OW certs are not the the same quality of diver that is going through the escape training. One last thing about escape training is that no ever expects to successfully use it. The BS of it "if you are trapped on the bottom you can get out" is not reality. Unless the rules have changes you cant even dive a sub shallower than 100 fm or 600 ft of water. The escape trunk was to give mothers at home a sense of comfort. the trunk was mostly made to be used with a DSRV for escape not an open water escape. OW does not train to do these CESA's to the level required to really be either a valid last resort or a useful one. Its done to jump through a training hoop. It is incompatant to give some body a 2 day class hand them a cert card never being deeper than 25' and say they are good to 130 however we recommend that you don't go past 60. The part of no deeper wit out training or experience means nothing either. Who verifies that the experience was the proper experience to make you compitant to go to deeper depths? At least there are AOW certs whether useful or not to say they have been on an experience dive to deeper depths and deemed qualified to do so per the opinion of a qualified diving trainer. If a diver is truly safe to do deeper dives than give an instructor a C note and have him give you a card that defines diving in a more dangerous environment or depth. Its sad to see new AOWs with temp cards and perhaps 10 dives to 30 ft, who still have a temp OW,,,, on boats going to 100+ ft.

A shhort story. In 75 I was assigned to go through the escape trainer bit did not get to . When i got on board i got introduced to what was called a steinke hood. an escape device to leave the sub and get to teh surface. it had a hood that inflated by opv's in the device to allow yo to breath from the bottom to the surface. I was chastised by those that taught it and the command as well for pointing out theat the inflation device was a CO2 cartridge and yo cant breath CO2. Not till a near death occurred in sub school with that very appliance did they remove the CO2 inflation fleet wide form the vests.

navy submarine steinke hood

 

[NAM001]

Submarine Escape Trunk and Survival Suits

go down about about 10" and select ehe second video abour Steinke hood rolled out about 2 minutes.

Here is a link to the Steinke hood look at about 1:02 and the fitting shown replaced the CO2 inflation device. the collar would fill and the OPV's under the face hood would vent the gas in the collar to the hood to breath. It was a death trap. I can only guess that when first made the inflation was done with air cartridges and not CO2 cartridges. These were used for years unquestioned for fear of rocking the boat until in the escape traiing tower a demonstration was being done for I think a congressman etc and they actually used the pull the string and inflate form the CO2 cartridge and found the diver could not breath the gas. The tragedy is that it took a near death to do something about the obvious.

 

[John C. Ratliff]

My OW instructor's follow-up was but you will be highly motivated to get there.

As I recall there's about 2 litres of stored oxygen in the body and only some (30%?) is in the lungs -- that's after breathing uncompressed air. ISTR it should be enough to keep you going for a minute. ICBW, mis-remembering, and all that, of course. One should be able to cover more than 20 m in a minute, even in gear with all of its drag. I would not want to try that either, but 40 m should be doable though extremely unpleasant. With a high risk of DCS unless it's the very first dive of the trip and you splashed with an empty tank.

dmaziuk,

You are only partially correct. Air volume is measured in liters in the lungs, but not in the body. In the blood stream, it is measured hemoglobin saturation. In the lungs, you have a "residual volume" of air, which is air which is there after a full exhalation. The below chart shows this:


From the U.S. Navy Diving Manual, March 1970.

Note that if the diver is breathing hard, and exhales completely, there is still 1.0 to 1.5 liters of air in the lungs. Let's say that (s)he is at 99 feet depth, which is 4 atmospheres absolute (surface is 1 atm absolute). If he starts ascending from that depth, the 1.5 liters will grow as the depth diminishes. At the surface, that 1.5 liters will have grown to 6 liters, but start growing slowly at first, and the last half of that will grow in the last 33 feet. The same holds true of the air in the diver's tank(s), in that it will grow as the diver ascends too. Therefore, at least a breath or two is available on ascent from the tanks.

I hope this helps concerning the ascent.

When I was an instructor, there was no "deep" certification. We taught sport divers to dive within the no-decompression limits, and that table went down to 130 feet (39 meters) for five minutes (including descent time). The NAUI Dive Tablen from 1990 had these points to remember:
--Consider all dives made shallower than 40' (12m) as 40' dives.
--On any dive, ascend no faster than one foot per second.
--For maximum dive time, make all repetitive dives shallower than your previous dive.

We did dive to 130 feet, but those necessarily were "bounce dives," and we discouraged divers from doing these deep dives. Most interesting things were seen between 60 feet and the surface in most dive locations.

My deepest dive was 210 feet in Warm Mineral Springs when I dove on that project with Sonny Cockrell and Larry Murphy, I think. The reason I say "I think" is that I had one dive in 1968 for search purposes (a helicopter had crashed) off an island in the Ryukyu Islands near Okinawa. We started descending where an eye witness said the helicopter had gone down, and stopped swimming down after about five minutes. We gathered, and compared depth gauges; each read differently, from zero to 200+ feet. We aborted the dive without seeing the bottom. But this was a military dive as an USAF pararescueman. I don't advocate deep diving, and feel that sixty feet is a great depth for most divers.

SeaRat