Wednesday, December 10, 2008
So, what are the roles and responsibilities between diver and blender ? The rules and regs are simple enough. The diver is responsible for analysing his gas when he receives it. The blender is responsible for ensuring the person filling has completed an official blending course (including the exam) and that the diver signs for his gas.
The problem is that we all get to blase about it...and stop following the process. It is a pain for the blender to complete a log, the divers complain about the delay... and invariably blending is delegated to a low ranking employee who may or may not have the proper, official qualifications. All round it is a disaster waiting to happen.
Diver do not make it easier either. We had the instance the other day with a new client arriving to have Trimix fills. It was a bit of a last minute thing (as it somehow always tends to be). When Gerhard examined the tanks he discovered they did not have any markings indicating that they were oxygen cleaned. G phoned the client asking what the status was. The client was a little annoyed... what was the problem ? G explained that we do not fill cylinders without oxygen cleaning and if we do not know the tank, we will oxygen clean them ourselves to make sure. His reply, what is the problem ? It is only a small amount of oxygen you are adding. I started to have a small fit. Why ?
Well last year we had a small oxygen explosion, from a cylinder that we knew and trusted. Gerhard walked away slightly deaf and with a nasty burn on his arm. Did I mention that this was a cylinder with all its paper work and a diligent, trusted owner ?
The long and short of it was that the client was told that if he wanted us to fill his cylinder he would have to get them oxygen cleaned, either by us or someone who was qualified. For some reason he battled to grasp the concept that his R40 nitrox fill (ok, there were some more expensive trimix fills as well) was not worth Gerhard's life. And that is really what it boils down to.
As divers we do not want to be bothered with rules and processes. So here are a couple of things you can do to make the system work
1) Have your paperwork. Cylinders that are nitrox filled or trimix filled need to be oxygen cleaned by a reputable vendor
2) If your cylinders are filled at the coast they require an oxygen clean before you fill them with nitrox or trimix again. In fact, if you are filling with any sport shop you should get them oxyen cleaned before using them for mixed gas again. Simply put, clean gas is not easy to find and it only takes a small amount of oil to kill the blender.
3) Give the blender time to fill your cylinders. It can take 2 hours to do a Trimix fill and the more rushed the blender is, the more chance for errors
4) INSIST on signing for your mixes when collecting them from the blender and ALWAYS ANALYSE even if it is pure oxygen. If the blender is reluctant for you to sign remember he is legally bound to perform this check and if he still has no mechanism in place... create your own paperwork. If something goes wrong on the dive the first thing that will be examined is the mix in your cylinders... and it starts to get ugly when fingers are pointed at the person who blended...you... the person who placed the cylinders. So why not avoid the whole ugliness/
5) Take your own life seriously. Is it worth R40 (a nitrox fill), R500 ( a trimix fill ) ????
Lastly, I would like to wish everyone a spectacular festive season. We are off to the bush for three weeks and the blog will resume in the New Year.
May the bubbles be kind to you :)
Wednesday, November 5, 2008
The study had two criteria that had to be met for a product to be recommended for use:
1) The product had to exhibit an absence of components that would case undue risk to human health during use that could not be prevented by reasonable protective measures
2) Proof had to be available that the disinfectant was effective
Interestingly, the report showed that 7 products commonl used were unacceptable. These were:
- Buddy Clean (gulp)
- Confidence Plus
- Sanizide Plus
- Advance TVE
- Bi-Arrest 2
- Listerine Antiseptic
Only two products were found to be fully acceptable, Virkon S (the product of choice) and Trigene II. Unfortunately at the time the study was released there was no version of Virkon available for human use (its origin is agriculture). There is now Virkon (without the S)
Some info on Virkon:
- It has been extensively tested and proven tot be a broad spectrum disinfectant, considered bactericidal, virucidal (both enveloped and non-enveloped), fungicidal and a tuberulocidewhen used at its intended working concentration of 1% for a min soaking time of 10 minutes.
- It comes in a number of package sizes.
- It is no deactivated by detergents or hard water, but may leave a residue if recommended decontamination procedures are not followed
- If used as prescribed, it is not deleterious to the health or equipment of divers and is effective against almost all microorganisms to which a diver may be exposed.
- Extended soaking of metal objects may cause corrosion/ damage and deactivation of the product more quickly (recommended soaking time is 10 minutes).
- A 1% solution is table for a week.
- Good infection control practice indicates that disinfectant solution should be changed daily, but this is unnecessarily wasteful. If the solution loses colour within the subsequent 7 day period it should be replaced
Interestingly ANDI and Juergensen Marine recommend a standard solution of 1% beta-dine solution for disinfecting.
If you are looking for alternative, here is the list recommended by ANDI (in order of preference)
- Virkon S (the agricultural version)
- Trigene !!
- Microban Disinfectant Spray (an ANDI product)
- Commercial Hospital Use disinfectant solution such as Beta-Dine 1
- Buddy Clean
- 10% Bleach Solution
- 50% Vinegar, 50% water
Based on these findings, Liquid Edge is importing Virkon and it is way more affordable than our usual products. Try one tablet that makes 0.5 litre for R30!
Friday, October 24, 2008
First things first: cells becoming current limited is a huge reality, can happen for sure! Remember they are one of the weakest links in your re breather. So what to do....
Looking at how the unit calibrate:
When you hit the "yes" button, the display you are looking at is the milivolts divided and measured against air in Oxygen. So to give you an example , one for altitude , one for sea level.
Sea Level: assume ambient 1 bar. Air= 0.21 , O2= 100% Calibration starts and the displays read : 1.02 1.00 0.96 What the unit does now is compare the mV reading to air whilst being in O2 , thus ACTUAL mV will be the following:
1.02 will be basically 10.2mv (thus the inspo now uses a set MV for start calibration assuming about 4.7- 021/100% oxygen- as its linearity checking) so the real MV of the cell submerged in O2 will be 10.2 mV * 4.7 = 47.94 MV , and that would ASSUME the start up MV was 10.2 as well ( It assumes Cell linearity is constant) NOW if you kick the lid off and measure cell 1 with a mV meter and do NOT get a reading of 10.2mV in air.... oops then the assumed linearity is incorrect....more about that later!
The Cell should be kicked out if it falls below 8.3mv approx (39.01mV)
The Hammer boots out ANY cell that does not make 40mv actual as it is predicted to become current limited(including at altitude ,which is a
At altitude the same applies EXCEPT that you must take the MB reading into
Thus if your reading is 0.89 0.88. 0.91 at altitude with a 850mb reading then just multiply the resultant by 0.850 to take it to "altitude"
Thus cell on will be 8.9mV * 4.7 / 0.850 = 49.2mV SEA LEVEL , or 41.83 Altitude reading- good stuff.
So even if you do not see a 1.00 when calibrating at altitude it does not mean the end of the world. According to your altitude it should be fine (above 40mv) SO if you work out the actual MV and see it is below 40mV actual for the altitude regard it as suspicious
NOW what I do NOT like is the fact that it works on a constant linearity assumption when you calibrate( 100% / 21%=4.7). So if you look at an actual as in the hammerhead you have the following:
At sea level my cell mV read in air : 10 9 9 After dousing it in pure O2 for calibration they all stabilize at 39 48 43 mV respectively.
That means that the ACTUAL linearity is as follows :
Cell 1 - 3.9
Cell 2 - 4.8
Cell 1 - 4.3
Thus you can see that it is NOT an actual constant and also cell 1 that seems high did not actually make the calibration and is now booted out as a possible limited cell, but the inspo will calibrate this cell as acceptable (borderline but there) esp if you told it the O2 content was 98%......
At altitude I expose the head to air to see the PO2 shown to verify air:
The mV reads 10 9 9
The Po2 I expect to see is .21 * 0.850 mb = 0.178 PO2 actual that the handsets should display.
All cells displayed within that range since previous calibration.
I wrote down my mV in Oxygen from the previous dive which was 39 48 43
Thus at altitude with pure O2 I expect to see a PO2 of 0.85 shown for each cell.
They all get very close to it.
You can then look at the linearity from each cell then vs now.
So cell 1 is 39/10= 3.9
Cell 2 is 48/9= 5.3
Cell 3 is 43 /9= 4.7
If you calibrate now and all values are still within that linearity level the cell is shown to be constant within calibration range. So if you DID fitness test the cell on the previous dive at 6m and it passed and now linearity check and mV seems stable the cell in theory should not be a problem as it's linearity range did not change (you can only hope!)
Also , in theory it also this tells us is that the cell showing highest linearity should be the most accurate in response range as it can read over a finer scale , no it does not mean it might not be limited, it just tells me the response range is the widest. It is like looking at a 300bar gauge vs a 400bar gauge. The 300 bar gauge will show clearer needle movement across the board as it uses a finer scale. You can see 2bar movement more clearly on the 300bar one than on a 400 bar gauge. So I would expect cell 2 to react nicely during flushes and O2 additions with cell one maybe a bit slower.
Use an approach where you can see yourself what the actual mV in air and actual PO2 is in air in regards to the previous calibration, and once the unit or cells are flooded with O2 then you can record that mV and PO2 shown BEFORE calibrating again. If the linearity is within the same limit the cell should perform in the same fashion ,esp if it is a few months old. You will at some point have 3 new cells in your unit ,it is unavoidable sometimes , but they need to be checked vigilantly esp in the first month. The hammer you can also leave flooded with O2 and come back after a while and look at the ACTUAL mV of the cells to see if there is any deterioration in the actual voltage. If there is , flood with O2 again, if the cells do not come back to previous max mV then get worried! The only way to test if it is current limited is to actually pressurize the unit on the surface or dive to 6m then spike it, deeper would be great. Problem is you do not want to start a heavy dive with an O2 spike through the lungs;-) But you can always go O/C , flush at 8 or so meters while manually manipulating the lungs to try get O2 cycled , look at the readings , then flush again and get on the loop and continue the dive.
Now this all sounds very good , but lets get back to the BUT... There are two options, one is single point calibration- so we use high o2 or 100% O2 to calibrate the cell, OR we try 2 point calibration, so we assume x linearity in air and x in O2 and draw a line, sounds good...and here is the BUT. Cells are NOT linear, they have a curve! The further away the maximum or minimum extends the worse the curve slopes, so your most accurate reading is the CLOSEST POINT TO CALIBRATION. In other words, if you calibrated at sea level- Po2 1 - then your most accurate readings should be in the 0.7-1.3 vicinity, if you calibrate at altitude- Mb 850- then all cells read Po2 0f 0.85.... hmmm...then reaching 1.3 is that little bit harder... Remember cells are usually within 2% error margin of calibrated value, so the only solution to check high end readings is to test the cell in a hyperbaric scenario. 2 Point calibration is not helpful either as I showed you with the hammerhead cells in air and O2 as the actual linearity differs, and as explained on a single point calibration you have a higher reference point from which to work, thus a smaller error margin...wow..!
Next option- Have cell verification like what was designed for the new Cis
Lunar- For those who do not know: It has only 2 cells ,one is the master and has a pure O2 and a diluent (air) injector close to the cell face. Approx every minute the handset hands control over to the slave cell and test fires a small amount of O2 at the master cell and a small amount of Air, it then looks at depth and if the cell does not show correct Mv for the depth the dive is aborted, so a constant hyperbaric test while diving, VERY cool...
except.... when testing was done on various other units ,they found that when blowing on the cell face you are faced with a few issues : If there is condensation on the cell face it sometimes helps to decrease it (yay!) , OR it actually blew moisture past the membrane into the cell causing.... yes you guessed it horribly incorrect readings. And guess which one manifested itself the most ? The latter of course.
The second fun problem (had one of those) is when you get a cell stuck. That basically gets a layer of moisture onto the cell face, it traps O2 behind the water ,and the cell only sees that O2 reading ,which is usually
setpoint. Now the computer sees 1.3 1.3 1.3 while you are happily
breathing the loop down and die embarrassed...or finally, when the O2 behind the cell face gets metabolized then it will fire the solenoid... oops, hopefully you are not an idiot and do realize when your solenoid did not work for a while, or your lung volume breathes down etc... The cool thing is if it was close enough to fire the solenoid before it got stuck it might be within range to start firing and of course will not stop firing the O2 in as the cell cannot see it... he he.
So what to do.....
IMHO ,only other possibilities :Nr 1= FLUSH YOUR UNIT OR GO O/C if you think there is a problem!!!!! The ONLY reliable piece of hardware is the thing between your ears we all assume is a brain ;-) Roll cells over (BEST), if you passed a fitness test on the cells within the previous 24hrs they should be good in theory, buy a cell checker from Narked at 90 (not really worth it-can built one way cheaper- 600 Pound Sterling!) or start diving at the setpoint where calibration passed (yeah sure!) Check your cells and record linearity if possible, but as stated that will just help you to identify if a cell seems to be performing in the same fashion as the previous dive, and where to expect a slow or fast reaction. The chances of loosing 3 cells to current limitation at the same time is VERY slim indeed! But be careful of exposing and leaving the cell in excessive heat or freezing it. Use a system that independently calibrates the cells and does not "take "readings from another. Use a 4th cell if possible.
In regards to cells, AP always claimed a better and more stringent protocol when verifying their cells, seems there might be a small hiccup. AI ( Analytical Industries) makes most of the cells. I have had as many AI cells fail as PSR cells as AP cells. Once again. Roll cells over, check linearity yourself for interest. You can clearly see how an assumed linearity can produce interesting readings. Just use bit of common sense and remember :
the job of the re breather is TO KILL YOU! Your job is to make sure IT DOES NOT!
If you weren't confused before , I hope you are now ;-) Cheers for now.
Tuesday, October 14, 2008
I doubt the answer is simple. Good divers start off with the ‘right’ tendencies that a ‘good’ community will re-inforce. Conversely, bad divers will be influenced by the community in which they find themselves. And there is that word again, community. The diving community is a complex animal, made up of divers, equipment suppliers, dive sites, operators and of course, the agencies. They are all interlinked, but some have more influence than others. A dive site/ operator that does not enforce standards by banning rogue divers creates an environment where there are no consequences and so allows other divers to start breaking rules. Their influence depends on the number of options out there, so dive sites have more influence than say a dive operator who has to compete with a number of similar operators and so is probably less inclined to be concerned and drive away paying customers. Then come the divers themselves, who get to choose to stand up for standards and make it known when they are broken and that it is not OK to do so. Their effect is also variable and often creates cliques of like minded divers who are hard to break into. Finally come the agencies. Now, as an agency your job is to create skilled divers. These divers become your brand, your face out in the world if you will, which implies that an agency should be carefully monitoring its divers and ensuring that they are in fact representing the right image. One would expect that agencies (both sport and technical) would pro-actively discipline its divers and instructors when they flagrantly violate the rules and standards. But they seldom do which creates an impression that (once again) this behavior is condoned. The result is that we have created a community where there are simply NO CONSEQUENCES.
So I was pleasantly surprised with ISDA. For those of you not on the chat list, this is a new, local agency that has received a lot of flak for breaking away from the older, more established agencies. It now has the unenviable title of being a rogue agency. Johan Beukes (a controversial figure in himself) decided that he was fed up with the lip service being paid to standards and to the poor quality of diver that was being created by our locally established agencies (both sport and technical), so he created his own. The recent incident where a sport instructor took open water divers on what is a full Cave, Trimix dive saw the usual blame shifting… except for ISDA, who suspended the open water diver who did the dive! In fact, they recently suspended an instructor for taking experienced open water students to a mere 40 odd meters in open water. ISDA divers know that they are their agencies brand and their agency is serious about its standards. They now know that if they break those standards there are consequences, which means that there are probably going to be a whole lot less standards being broken by those divers. Which leads me to ask the question, isn’t it time that the old, complacent agencies started to catch a wake up! Here is an agency that takes its standards and reputation seriously. Here is an agency that understands that its reputation is based on what their divers actually do AFTER the course is over!
I find myself asking the question, should I be paying more attention to ISDA and getting involved ? It would blow my neutral stand completely….but maybe it is time to stand for something, rather than against something.
We are the diving community ! Who you are and the service you demand from agencies and dive sites is what has created and what will create the community in which we dive. If you want to improve the standards out there, you need to commit to creating an expectation of action from the agencies and an expectation of compliance from the divers. And while that happens, I am going to start paying more attention to those so called rogue agencies!
Wednesday, October 8, 2008
1971: A diver from Wits Underwater Club died after a free ascent. The diver was using a cylinder with a reserve valve (J-valve), and no SPG. The J-valve usually had an actuation rod / pull rod down the side of the cylinder, to allow the diver to pull the reserve lever. In this case the diver did not have one, and was unable to access the reserve. He tried to do a free ascent, but suffered from pulmonary barotrauma. I spoke to Roly Nyman about this one years later, and he added a detail that is quite relevant to divers even today. The victim had done many dives with the cylinder, without the reserve rod, and always been able to actuate it. On this particular weekend he was diving in a brand new wetsuit – apparently a birthday present. The wetsuit was far stiffer than his old gear (probably a thick rugby jersey, knowing the times), and on this occasion he was unable to trigger the reserve. Even small changes in equipment can have a major effect. Don't take untried equipment on a deep dive.
1975: A diver died during a club trip with the Transvaal Sub Aqua club. I was later a member of this club, and had access to all the old records. I also spoke to older members about this accident, but no-one could shed much light on what actually happened. The diver had been trained overseas, in Germany, and had never dived with the club or in South Africa before. He was also suffering from flu at the time. The club Diving Officer advised him not to dive that weekend, both because of his condition and because the DO was not happy with his training records. The diver decided to go anyway, and the club took a “it’s your risk” approach. Afterwards this was a major discussion point at the club, and the committee minutes in the aftermath note that the club would, in future, be more “positive” in controlling who could and could not dive. In terms of the actual accident, it appears that the victim lost consciousness and drowned. Whether it was narcosis, medical, or a combination was uncertain.
1977: A bad year at Wondergat. Early in the year a diver from Eskom Sub Aqua died. Again the details are not too clear, as he separated from his buddies. His body was later found on the bottom.
Later in the year two divers from Wits Underwater Club died on a night dive, Wondergat’s first double fatality. The divers had been doing a shallow night dive , using a line and float to keep them at a safe depth, and out of overhangs. The club also had a surface marshal, logging each group in and out. The two divers surfaced after the dive, a few metres from the entrance. The surface marshal logged them as surfaced, but then some time later noted that they hadn’t climbed out. There was no sign of them at the water, or at the camp. A search was launched, and the bodies were recovered from the bottom. According to the theories on this accident, the two divers decided to swim underwater from where they had surfaced back to the exit point. However, on descent they managed to pull the surface float underwater, and ended up going all the way down. Inexperience was certainly a factor in this accident. It is also important to see how the systems they thought would protect them proved inadequate.
1983: The Niewenhuizen twins. Probably the most talked about accident at Wondergat. The twins were on a night dive, linked by a buddy line and with a single torch between them. At some point they separated from the group, and lost the single torch. The torch bobbing to the surface was actually the first sign that the rest of the group had of the problems. The bodies were recovered from the bottom the following morning. Although there was a lot of criticism of the dive group for allowing two divers to share a torch in this manner, it was not an uncommon practice. My first night dive at Wondergat two years before this was in exactly the same situation! It was only after this that it became an absolute rule that each diver had to carry their own torch.
1984: A diver died after becoming entangled in a rope near the grid during a night dive. I never got many details of this accident, as it involved a dive school at a time when there was tremendous animosity between schools and clubs. The dive school later denied that there had been an accident, my only lead was that I knew the divers who did the body recovery.
1985 or 1986: A diver from the RAU club died in the main cave. Again many details were unclear as the victim had separated from the rest of the team. His mask was found some distance from his body. There was speculation that he’d lost his mask, and tried to do an ascent with his eyes closed, or at least with minimum opening. He is thought to have hit his head on the cave roof and lost consciousness as a result. Nuno Gomes and Malcolm Keeping recovered the body.
1991: Dick Grace incident. A very experienced instructor (Instructor Trainer) was killed during a deep rescue. I haven’t got the full details, I was living in the UK at this time and only heard about it much later. As I recall a student also died. The whole dive was basically a mistake – inexperienced divers being taken too far. The fact that the leader was a very well experienced and qualified diver didn’t prevent the accident, the leader was killed trying to rescue one of the victims.
1996: A free diver died, presumably from breath-hold blackout. He had been free diving to the bottom of the main shot line, was seen to surface and then immediately sank. Sadly this took place right at the end of a weekend, so all scuba gear had already been packed away. By the time a team could be kitted up and sent down, it was too late. Despite lengthy resuscitation efforts, the diver died. The diver in question was very experienced, but perhaps showed poor judgement by free diving so deep with no cover available.
2004: A lady diver died during a dive. From what I could gather, the victim had a medical problem that resulted in her losing the regulator. She subsequently drowned before she could be rescued.
Wednesday, October 1, 2008
Last weekend a young sport instructor (who only recently completed her Advanced Nitrox course), deemed herself fit to take an even less experienced diver (open water 2 I believe, so what, 20 dives ?) to the back of the cave at Wondergat. This is a cavern dive to 52 meters. It looks easy. First you descend 35 or so meters to the cave grid. Then you head off on one of the permanent lines, down a fairly sleep slope that slowly levels out as you enter the gloom of the cavern. If the vis is good you can see the whole cavern mouth from the back. Normally the vis is trashed thanks to inexperienced sport divers speeding in on short bottom times (to avoid decompression) and with inadequate buoyancy skills.
This is not the first time that this instructor has done this. Last time a complaint was lodged with her agency (nothing happened) and she was talked to by experienced technical instructors so I can only conclude that she sees nothing wrong with her actions and deems herself to be a superior diver that can manage any situation at any depth with any number of following divers. This is interesting because one of the fatalities from the back of the cave was a highly experienced national instructor who took open water 2’s to the back of the cave and paid for it not only with his life but also the life of one of his students (the student was on a single cylinder and ran out of air at the back of the cave. The instructor was on twins. They both ran out of air before reaching the mouth of the cave).
The thing about Wondergat is that it is deceptive. Going in is easy thanks to the slope which means that there is little effort involved. Going out is a swim thanks to that slope. This means divers are having to work, which increases gas consumption… all of which is a recipe for disaster. Especially if the divers are sport divers with marginal buoyancy (yes, pretty much every diver we get thinks they have buoyancy control but turns out when they have to do the standard technical drills they do not), sport equipment (one cylinder, one first stage, no back up gas, no decent lights) and no gas planning. Oh yes, and no experience or build up to mitigate narcoris.
I have a number issues with this dive. Firstly let me point out that this lady is not the only instructor doing this. She was just silly enough to brag about it on the net, so she gets to be the lesson.
My first is the arrogance of instructors who think that they are capable of dealing with the situation just because they are instructors. That is the kind of attitude that has killed people in the past and will kill people in the future. It is called ego and it seems that women are not immune to it. An instructors does not give you immunity or god like powers (and this applies to highly qualified, experienced technical instructors as well).
The second is the blind naivette of the student who believed her and followed her (see my blog on trusting experienced divers). As a diver you need to take responsibility for your own safety and not just trust divers who seem to know better. The odds are they do not! And you pay the price, often with your life.
Lastly, I am annoyed and concerned with the blasé attitude of sport divers and instructors who simply DO NOT KNOW how restricted their world is and break the rules without bothering to find out how. Now I guess that last statement could be deemed to be contradictory. After all, I am stating that I do not condone breaking of the rules (divers should not dive outside of the depth they are trained to) and then I say if you are going to break them at least know how ? Training is one way to learn how to break the rules. It is there to teach you what you do not know and how to to safely extend your limits. It is not the only way to learn however it is the safest.
I should at this point say that there is a reason PADI does not have courses that take you deep…depth changes the rules significantly. Sport diving teaches you to dive on a single cylinder with no decompression. It does not teach proper dive planning, proper gas management, proper buoyancy control and any appropriate risk assessment or management that will allow you to undertake a deep dive safely. Why ?Because that is not what sport diving is about. Sport diving is about the path of least resistance. It is about the least amount of knowledge that will get the most people divin, safely enough to avoid legal action (perhaps a bit cynical, but not so far from the truth). That is why technical dive training exists.
So, why is the back of the cave so different ? And how would a technically trained diver do things differently ?
The first hurdle to get over is the anti-air brigade. It has become kewl to diss air and recommend Trimix. Yes, air is bad and yes, you should be diving Trimix. The problem is Trimix is not always available and when it is, it is ludicrously expensive (think R600 for a dive). Based on these two facts alone, air is NOT going to go away easily. Add to that the fact that air is easy to come by never mind easy to breathe and there is no real hard limit to stop a diver from just going deeper and deeper. Now throw in the handy dive computer and any limits a sport diver used to have disappear entirely. They don’t have to think! They don’t have to know anything about decompression. All they need is a full cylinder and a dive computer and they can go anywhere for as long as they like…… or so they think.
If you are going to dive air you need to understand the characteristics of air and the risks entailed so that you can actively PLAN for these. In a nut shell dive planning firstly identifies what risks are unique to the dive you are doing. Then it allows you to consciously determine if you can avoid these and if not, how you are going to manage them. All dive planning amounts to ensuring you have enough gas to breathe for the whole dive (and never touch your reserve), you have enough light to see by, you have the mental ability to think and that you can manage any probable situation underwater.
For the back of the cave the list has things like:
- Narcosis, it is 50m
- It is dark, and gloomy so if you lose the line you are lost
- It is dark and gloomy, so your narcs is going to be higher as you are going to be more stressed
- It is at least 5 minutes (that is optimistic) from the surface, probably more so what happens if you have a dv failure, or blow an o-ring ?
- It is going to take at least 5 minutes to get there, which means you have descended at speed, which means your narcosis is going to be way worse.
Lets look at narcosis first!
Now every diver thinks they know about narcosis. But what do they know ? That it starts at 30 meters ? What divers tend to be unaware of is that the increase in narcosis with depth is not linear but rather exponential. Narcosis at 50 meters plus is very, very different to that at 30 or even 40 meters. To give you an example - as an instructor with Wits Underwater club I regularly had over confident open water 2 divers who (because they had been trained at 30 meters) had NO respect for narcosis simply because they had never really experienced it ( 30 meters is the start of narcosis so the effects are hard to notice). I learnt quickly that talking about narcosis had not effect. The only time these divers got respect for how bad they are at thinking and ‘doing’ at depth was when they were deliberately taken on a dive designed to narc them out (that would be a fast descent to 35, 40 meters). Then and only then did some (not all ) of them realise how debilitating narcosis really is, which is the point at which they started to take it seriously.
The next thing you learn is that there is no cure for narcosis. If you dive deep enough on nitrogen you will always experience narcosis (adding helium only extends that limit, it does not cure narcosis ). To get rid of narcosis you have to reduce the partial pressure of the nitrogen in your mix, which practically means ascending. Acclimitisation makes a difference. In fact, divers who regularly dive deep air spend inordinate amounts of time training for deep air and acclimatising.
Now the concept of acclimitisation is in itself controversial. I am a deep air diver, so my experience is that if you build up for depth your ability to manage task loading (think and do) is greatly improved. In fact, if I have not dived deep for a while my first deep dive will be a nightmare. I am totally narced, so I spend as little time as possible there and get shallow as fast as I can. The next dive is normally better. My approach to managing high levels of narcosis is to slowly build up to them. What do I mean ? Well if I was to move from 30 meters to 50 meters I would spend a weekend just doing 30 meter dives -. 3 on the Saturday (all with decompression because it is time at depth that gives you acclimitisation) and then a 30 and 40 meter on the Sunday. The next weekend (not more than 2 weeks later) I would then do 4 40 meter dives. Only then would I deem myself to be fit to do a 50 meter dive (and then only if the dive is within 2 weeks of the build up sequence). On the actual weekend I would do a 30 and a 40 m on the Saturday followed by the big dive first thing on Sunday. Oh, and I would have had no alcohol for the entire build up sequence and be avoiding things like caffeine and coke.
There are two other aspects a technical diver would look at, having the right equipment and being 100% familiar with that equipment. Being familiar with equipment means being able to lay your hand on a dv or a cylinder or a fin or a knife within seconds of thinking you need it… without spending valuable seconds searching for it. It takes effort and lots of practice to build up that kind of unthinking familiarity with your equipment.
Which brings us to equipment. From our dive planning we know that this dive is at least 10 minutes, if not 15 minutes long which means gas is going to be a concern. It is also deep, so you are going to be using more gas than on your normal 20 meter dive. You are also going to have to swim, are going to be narced and it is dark and guaranteed as a sport diver that means you have insufficient light (last Time I heard this dive done with one torch between 4 divers), so you are going to be stressed. As a technical diver you know what your gas consumption rate is so you can work out for a 15 minute bottom time (that means leaving the surface, getting to the back to the cave and leaving on 15 minutes) exactly how much gas you are going to need.
You are also not working on a standard 50 bar reserve rate, but on critical pressures (which is a whole blog on its own). In a nutshell your critical pressure is the number on your spg at which you must turn around. If you turn around when your gas content gets to that pressure you have enough gas to get you to the surface and still have 50 bar left. This is completely different to the sport divers who turn around on 50 bar without knowing if 50 bar is enough to get them to the surface. The assumption is it is and in most cases that is true, because they are diving within very tight limits. Another difference is that leaving on 50 bar means you are still using gas to get to the surface and are planning on reaching the surface with 20 bar. We plan to reach the surface still with all our reserve…totally untouched. If you are not using critical pressures (which requires conscious dive planning), you should be using at the very least the rule of thirds, i.e. you breathe a third of your gas mix into the cave and when that is gone REGARDLESS OF WHETHER YOU HAVE REACHED THE BACK OR NOT, you turn around and come back out.\
There is a good chance that calculating your actual gas requirements will indicate that this dive is NOT feasible on a single cylinder. In any event, as a technical diver you always have at least two cylinders with you. There is a very good reason for this and it is called redundancy. The last place you want to lose your entire gas supply is at 52 meters. Now every good sport diver just shrugs and says, my buddy is right next to me…except he is stressed and sitting at 80 bar, so now you have to get two divers all the way out of the cave on 80 bar ? Not a situation I would rate my chances in. Sport rigs also have only one pillar valve, which means if you blow an 0-ring or have a problem with a first stage you lose BOTH dv’s, the octo as well. Not a situation I would like to be in at 52 m with only a novice buddy to look to for assistance.
At the very least on a dive like this every diver should have access to staged gas. They should be carrying it with them or have placed it at the grave stones and then the cave grid and still they should have something with them.
This is the abbreviated version of a dive to the back of the cave. It does not even touch on decompression, just the basics of making sure you are not narced out of your tree and have enough gas to get yourself and a buddy all the way back out again. There is simply no way I could put into a single blog all the information you would need to be able to do this dive safely…which is why we have technical training. It is also why I will strongly berate divers who do this kind of thing. If you take only one thing away from this, let it be this…. It is never what you know that kills you, it is what you did not know…and what you did not plan for…..oh and sport diving is highly, highly restricted and limited.
Monday, September 22, 2008
One of the bigger challenges with starting technical diving is the kit! Gone are the days when a dive required a single cylinder with any dv and a any jacket bc. Technical diving is about leveraging science and equipment to safely extend your limits and that means a whole new look at equipment.
One of the first things we tell people is, do not buy your equipment before the course without chatting to us first. And the reason is not because we want the gear sales, but rather we find that people often arrive having spent a small fortune on kit that is simply wrong. Within a few dives (if not during the course), they find themselves hastily putting their kit onto the second hand market so they can get something more appropriate.
Getting the Basics in Place
This is kit that you should be acquired before anything else.
- At least one dv (there really are only two brands that compete, Scubapro (my preference) or Poseidon which is Nuno Gomes’s preference).
- Two SMB’s (one red, one yellow)
- A long hose for your dv (this means 2.0 meters)
- A wing and a Backplate (try Frog for value for money).
Total additional outlay (excluding the dv) is in the region of 4.5k. Some of this can be rented, such as the wing and backplate, but as harness sizes can be quite specific it is often best to put that on your priority list of things to acquire.
At this stage the dv is not critical, so you can re-use what you had for sport diving. If you did not get around to acquiring a dv, then you can rent until such time as you do get there.
Filling in the Blanks!
Once you have the basics, then you can start to make additional purchases. Obviously the order of purchase is going to depend on your budget as well as your depth goals. Here is mine (in order of purchase)
- Dry suit ( there is no point in having all the gadgets but freezing your butt off doing long dives) (+/- 10k)
- Your own torch/ light (something along the Sartek line, i.e. canister light with 10W HID light head) (+/- 6k)
- Another dv (secondary) and if you do not have a high end dv (yes, I am going to say the word Scubapro here), this must be high end (+/- 7.5k).
- Your Own Twin set with isolation manifold (new +/- 9k)
- Trimix Computer (+/- 16k)
- Better secondary lights
- Proper Fins
- At least two stage dv’s (+/-4k each)
- At least two stage cylinders (+/- 2.5k)
- More cylinders, more dv’s
- Another computer (you should have two)
- A booster for filling helium
Some of this list is easier to rent and most people only add stage cylinders after they have acquired everything else. The most important aspects in my mind are having proper, reliable dv’s (my favourite is the Scubapro MK25 with S600 or X650 second stage, for stages I have the MK2 with the R380’s) and a decent dry suit. These take care of providing you with gas under any conditions and keeping you warm. Dive computers are really nice to have, but…you can (and should) be doing your dives on paper and not relying totally on your computer. I certainly would by a dry suit before I bought a computer.
Many people get put off technical diving because of the long list of kit that you seem to need. However, most of us acquired our kit over time and not all in one go. The bad news is, you never seem to have enough kit, especially if you start to push your limits and do more exploration. The good news….it is totally worth it
Thursday, September 18, 2008
The biggest complaint that most divers have in technical diving (well, in diving actually) is when will we all grow up ? To put it is a single word, Politics! This instructor is not speaking to that instructor, this agencies is not speaking to that agency, this one is slagging that one off! What is a poor diver to do ?
This came home to both Gerhard and myself with the current AED initiative we are trying to get off the ground! Now, we thought (naively it turns out), that the diving community might all pull together when it comes to safety! Well, yes and no!
First there was the argument from the coastal contingent, ‘Why should they support the inland dive sites ? They do not dive there ! (completely forgetting that the divers that come and dive with them at the sea are predominantly trained inland)’. We weathered that storm and bravely went on, to meet the next issue, ‘Why should I help out, the dive sites should manage safety, they should buy the AED’! Well, that one just blind sided us! Umm, because you are going to look really silly at a funeral blaming the dive site when all it took was one raffle ticket (or 5 if you are feeling generous) and 3 hrs to learn how to use the AED, but hey, maybe it is just me ? Maybe I am the only one that thinks that something’s in life are just to important to leave to institiutions and that you should just get off your butt and take responsibility!
Then it got even worse! Then we all (DAN included) got accused of playing politics! Questions were thrown around about whose name gets to go on the AED’s ? Why are we (Liquid Edge) behind this ? What do we want to get out of it ? Why should money be given to us ? How does he know where the money is going ? What if we steal it ? That one had us stumped! How do you deal with that level of paranoia ? What was even funnier is that the only person who seemed to have an agenda was the individual preventing us from finding a way forward (and I still do not have a clue what that agenda was).
So I got to thinking, what is it about the diving industry that seems to promote petty politics ? Is it because it is perceived to be small and price sensitive, so that means every individual is in a dog eat dog world and has to fight for his piece of the pie ?
Is it a South African thing ? What do I mean ? Well, we all are quite comfortable sitting back complaining about how the crime is intolerable and why does the government not do anything about it, never even thinking that maybe we should let the government be incompetent all on their own.! Why not go around them and fix the problems ourselves ?
In fact, I have this sneaky suspicion that the country dynamics we live in are totally reflected in the smaller communities like diving. Anyone who is part of the scuba list will attest to the amount of cynicism and ‘fight’ that is part of the community! We just seem to be intolerant in general! And it all is personal!
As an individual I believe that who I support should reflect my personal value system, so there are individuals and companies that I simply will not associate with (Zimbabwe is a big one and yes, I know, how does me NOT going to dive Sinoi make Mughabe sod off ?). I have only one real vote and that is where I spend my money and time, so I use it! But here is the thing, that is my choice and I do not expect you to make the same choices! You have the same freedom of association!
Are we really so small and insecure as individuals that we can not see behind the names to the benefits that could be obtained if we just Got Off It! I am now going to get off my soap box! The point really is this, you don’t have to like me to agree that something is worth doing, and supporting a cause is not always about supporting the individuals behind it! We will never get rid of individuals, but we can get over politics! And as individuals we can start to be responsible for creating the communities we would like to live in! We can make a difference. It always starts small!
Tuesday, September 9, 2008
The incident did drive one thing home for both Gerhard and myself - how unprepared we are as divers for a medical emergency. You see, there is a device especially designed for lay people to use to restart a person’s heart. The site did not have one. No-one on site had one and it took the paramedics around 20 minutes to arrive on the scene with one. It is called an AED and it costs R16,500. My question to you all is, when some-one you love or even just know dies, would you not be prepared to pay that price to get them back ? I know I would!
We are now trying to get the diving community involved in ensuring that all dive sites (starting with the inland sites) have an AED on site. You do not need to be a paramedic to use it, that is the point. As a diver it will take only 3 hours to learn on the DAN AED course. Me thinks it is time the diving community got involved and started to look after its own, rather than waiting for the government or some gracious donor to do it for us. So please watch this space. We are putting together a fund driving initiative with Underwater Africa, DAN, Scubapro and Submerge to raise funds to get one of these at Miracle, Bass and Wondergat. If you are interested in finding out more or becoming involved/ donating to the cause please e-mail me at firstname.lastname@example.org.
For those of you who are still undecided - here are some sobering facts from Gerhard:
Cardiac arrest is the most common way for divers to die. The most immediate "rhythm" post cardiac arrest is 90% of the time "ventricular fibrillation". The ONLY medicine for it is to defibrillate the patient. In CPR the only real purpose is to help maintain oxygenated blood to the brain to try and keep it alive in anticipation of a defibrillator becoming available. You have to use a defib to cure the patient.
The effect of delaying defibrillation is significant as a positive outcome is DECREASED by approx 7-10% plus for every minute lost. So every minute that passes on cpr we loose approx 10% viability… and that is with PROPER CPR in progress.
What is proper CPR ? Well even paramedics battle to get this to the level’ proper’. Properly performed, CPR has an approx positive bloodflow result of 8-12% in patients. So we are basically 8-12% as effective in moving oxygenated blood around the body as the heart is. Not a great number but very effective in maintaining oxygen to the vital organs. Here is the thing though, a rescue diver’s chances of giving ‘proper’ CPR are not good. In fact, most paramedics arriving at a scene where a patient is being resuscitated do not hold out much hope of a successful outcome (it is not a nice thing to say, but it is the reality, why rush ? the patient hardly ever recovers in these instances). A patient’s best chance is if he has a witnessed arrest (which is what happened in this case) as he then receives immediate professional attention. But without a defib or AED the chances decline rapidly.
The AED or Auto External Defibrillator was designed specifically for laymen where professional help is not immediately available and the patient has suffered a heart attack. The AED can identify some "shock able" rhythms and apply the necessary steps with voice guidance to the operator. It has been used extensively in the US on airports in a massive campaign and they are claiming very good survival rates. It is a course that almost any DAN instructor can do. The AED is virtually "Idiot proof" and has VERY low maintenance - the battery is non rechargeable (in some units) with a shelf life of 4-5 years and an operating time of roughly 50 shocks or 20 plus hours. Once the unit is used, the battery can be replaced at around R300. It comes with single use pads and a bag.
Personally, I am getting one for myself…for my family, for weekends away! We are already carrying Gerhard’s crash bag every where we go! So please, please, please, join us and get involved! Every diver makes a difference.
Wednesday, September 3, 2008
What do You Need Experience Wise?
Most technical courses require the following when it comes to certification and dives : at least 50 dives, a nitrox certification AND your advanced diver with deep specialty.
In essence technical courses are designed to create stepping stones that take you from the limits of sport to no limits. This means you need to learn:
- How to use gases to optimise decompression
- How to use twin sets
- How to use stages
- How to use a smb (surface marker buoy)
Once these basic skills are under your belt, you can add more advanced skills like cave skills (which really perfect your buoyancy not to mention add a whole new level of task loading….you now have a reel to manage and a light) and of course the planning and extra kit involved in Trimix diving.
The Starting Point – Advanced Nitrox
Technical courses all start from a single building block, Advanced Nitrox - however, whilst a number of agencies have this course, not all courses are equal and by signing up for an Advanced Nitrox you may not be able to proceed to the next level without an additional course. What do I mean ? TDI’s Advanced Nitrox does not include Deco Procedures (which is a separate course). So to be at the same place as the IANTD course you will need to make sure you also include Deco Procedures. To make it more complicated, not all courses have the same name (and as we just saw, the same name does not mean the same thing).
Adding Skills - Overhead
Once you have the basics under control (decompression, twin sets and stages) you can look at either progressing deeper or into cave systems or both.
Cave courses generally come in nice, easy to learn modules and you have the choice of cavern (where you just get used to being in the dark and can still see the light), intro cave or full cave. These courses are not sequential, ie. You can go straight from advanced nitrox to full cave (in fact, one of our more popular courses is the combination of advanced nitrox and full cave). Incidentally, if you are a sea diver and not so much interested in caves, the cave course is the best way to become a wreck diver, giving you the skills to tackle any wreck.
Adding Skills - Deeper
Courses that extend your depth will introduce Helium and may take you in steps from a Normoxic level (where you need a single helium mix that you can breathe from the surface) to Trimix (where you use a number of mixes during your dive). These courses introduce more detailed dive planning and gas management and of course, get you deep enough to find that elusive Coelocanth or explore that wreck(
When to Combine a Course!
In most instances you are able to combine courses and so optimise your time (and of course your money). The one course you can not do in comination is nitrox, that is a pre-requisite that must be in place. However, if you do not have your deep speciality, that can be integrated into the course you are doing.
Depending on your starting point and comfort you can combine:
- Advanced Nitrox with Normoxic
- Advanced Nitrox with Full Cave
- Full Cave and Normoxic
So, when you going to come over to the ‘dark’ side ?
YOUR GUIDE TO THE COURSES ACROSS THE AGENCIES
· Advanced Nitrox (Depth to 40m) (NAUI = Technical Nitrox plus Deco, TDI = Advanced Nitrox plus Deco, IANTD = Advanced Nitrox, ANDI = Level 2)
Note: For Naui you need 25 Nitrox dives to start and 75 dives to do deco
· Normoxic Trimix [Depth to 60m] (NAUI = Trimix Level 1, TDI = Trimix, IANTD = Normoxic Trimix, ANDI = Level 4)
Note: For IANTD and NAUI you need 100 dives (for IANTD this is a discretionary requirement)
· Trimix [Depth to 100 m] (NAUI = Trimix Level 2, TDI = Advanced Trimix, IANTD = Trimix, ANDI = Level 5)
Note: For TDI and NAUI you need 150 dives of which 30 are deco, For IANTD, 200 but (for IANTD this is a discretionary requirement)
Thursday, August 21, 2008
Getting started in tek requires a number of decisions on the part of a prospective student, not the least of which is, ‘Where to go ?’ and ‘Which agency to choose? ’ Do you go NAUI, TDI or IANTD and what about ANDI ? Which is the best ? Which has the standards ? Which better materials ? Which better pricing ? Which better course structure ? Which is agency is for you and is choosing an instructor as important a choosing an agency ?
Within the South African technical diving community there are few full time technical schools that focus only on technical diving. Some sport schools do have an in-house instructor who can offer a limited selection of technical courses, but their focus remains on sport divers. Mostly technical instruction is done on a part time basis through part time instructors who offer technical training on weekends. This means that courses are few and far between and often take time to complete having to be undertaken over a number of weekends. Indeed, Liquid Edge is one of two full time technical schools in the country and the only company that is not affiliated to a single agency. Which is where we pick up flak, surely we should have picked one agency and should be recommending this above all others ?
Our non affiliation to any one agency has been an active choice on our part. Our aim has been to provide a single point of contact for divers that crosses all the brands and in so doing provides the client with the ability to choose the ‘right’ course rather than the ‘right’ brand. Indeed, a large part of our goal as a company is to promote technical diving as a whole, regardless of who you end up choosing as an instructor, school or agency. This means we are the only school that has experience in technical diving across all the agencies (NAUI, TDI, IANTD and ANDI) at all levels of instruction (from nitrox, through trimix to expedition trimix and full cave). This means that as an instructor, Liquid Edge’s Gerhard du Preez has unparalleled exposure and experience which in turn means you get a holistic view of all the agencies… enabling you to choose the one that fits best for you (rather than the one we are punting).
There is another reason why we did not choose to represent a single agency… because no agency stands out from the others when it comes to actual standards (and standards are the first and most obvious criterion on which to make a choice). Of the list that we represent, there are only two agencies that are proactive about enforcing and protecting their standards – NAUI and ANDI both of whom do not believe in paper instructor cross overs and made Gerhard do the complete course, all aspects (including swims and breath holds). They also require two pairs of eyes on certification. So yes, we favour NAUI and ANDI from a pure standards view point, however there are other aspects that need to be taken into account as well, like existing brand loyalty (PADI and NAUI both generate students that are loathe to leave their brand) and of course quality of service and materials (books, c-cards etc).
Apart from their international standards, every agency has its own particular South African flavour that either adds to or detracts from our image and the quality of the service we provide when we interface with students. So, whilst we may favour NAUI and ANDI from a standards perspective we have to factor in cost (ANDI is more expensive) as well as the course structure (ANDI has more steps to get to the same place … which from a standards perspective is brilliant as you get a seriously competent diver, but it means it costs more and takes longer). Taking out ANDI, TDI, IANTD and NAUI have similar course structures so it takes about the same time to get an equivalent qualification. They also have a similar cost structure. Which leaves us with the quality of the materials and service that is available to us and our clients. Based on these criteria we prefer TDI as their materials are more what the average PADI diver is used to (professional and high quality).
Based on all of this, our recommendation is simple. If you are a PADI diver, then go TDI. If you are a NAUI diver, why change ? And if you are really sold on IANTD, then congratulations, we can provide you with excellent training that incorporates our knowledge of all the programmes in an IANTD format! In fact, when it comes to cave certification there is no single certificate that will guarantee that you can dive in any cave in the world which means that if you have an IANTD cave course you still need a TDI certificate and visa versa.
Indeed, I would argue that it is not so much the agency that creates excellent divers, but the instructor! What an agency gives you is a set of minimum standards that all divers with that brand will have. Good instructors add to the basics of their preferred agency giving you more than what their agency offers.
Tuesday, August 19, 2008
I promise that I will not cheat this week and do a small dive show feedback instead of an actual blog :)
Firstly thanks to all the guys who came to visit us on the weekend. We were hectically busy and it was really great to meet people who are visiting our web site and our blog. Our schedule is looking busy right up until xmas and I am looking forward to introducing a whole lot of new divers to the amazing world of tech. To follow on from the show my blog this week will focus on getting started with tech (as that was the conversation we had the most J ).
If there are any questions you would like more info on/ answers on please let me know. Safe Diving ya all :)
Tuesday, August 5, 2008
Yes I know… an entire blog on fins ???? Am I finally losing it ? Perhaps, but then again fins seem to be cropping up in my conversations these days. You see I am a fan of the Scubapro split fins… and Gerhard (active technical instructor and firm believer in Hogarthian that he is) believes in the more traditional jet fins. Now as you may have come to realize, I tend to view all dogmatic idealogy (especially in diving ) with circumspection, so I get totally suspicious when I get told that there is only one fin for technical diving. The burning question is, is there really a fin that is superior when it comes to technical diving ?
It seems that most instructors and die hard hogarthian (and dare I say it, DIR) divers prefer the jet fin. Owning a pair I have to say it can not be a preference based on pure appearance because they look bulky, uncomfortable, heavy and squat. It is basic, basic, basic with a lack of flexibility in the foot pocket that simply screams sore feet. They are also limited when it comes to colour choice coming in black, black or black (seriously, must all technical diving be done in black ? Can we not get a little more adventurous and maybe try something in navy ? Or heaven forbid yellow, green or even yes..,wait for it… pink ?).
The jet fin boasts a design that is at least 30 years old and a philosophy of sticking to the basics and keeping it simple. Being manufactured out of negatively buoyant rubber they are heavy, which is not a bad thing if you are in a dry suit as it eliminates annoying floating feet and ankle weights. Their manufacture also ensures that they are stiffer than most other fins which makes them feel like you are wearing a pair of planks but having said that this rigidity does mean you have far better control underwater. They are almost designed for modified flutter and frog kicks (which as you no doubt know are essential anti-silting techniques). Because they are extra stiff they are much better suited to high current diving (not really an issue for us South Africans) not to mention propelling heavy and bulky (read drag prone) gear through water both of which are a definite plus.
The jet fin also has one other element of design which proponents wax lyrical about, the straps. One of the first lessons I learnt as a technical diver was to tape up my fin straps to avoid them getting caught on lines etc. The irony of which did not escape me when I found myself with one fin caught mysteriously on the line at 152 meters. Truly the last thing I excepted to go wrong on that dive was getting trapped on the line and I ended up with the choice to either cut the line (which I was not happy to do being as I was in a confined space in a silt out… yes, I could use the walls and positive buoyancy to get out but the risk of getting further entangled in loose line was not appealing) or I could leave the find behind. Which I did. I still do not know what it trapped me…but one of these days I will go back and retrieve that errant fin and hopefully find out what.
Which brings me back to straps. The jet fins come with the most primitive straps you can imagine. In fact they remind me more of Sean Connery James Bond diving gear than the gear we are familiar with these days. Firstly there are no convenient plastic clips for getting in and out (which incidentally is how I got out of my stuck fin. I shudder to think of trying to remove that fin without convenient buckle to release). Instead, the strap connections are moulded into the fin. This means that there is no leading edge groove to catch on line. The straps are also arranged in such a way so that the ends are on the INSIDE of the rest of the strap. This presents a perfectly smooth surface on the outside of the strap and clip area so entanglement is virtually impossible. The down side is that they are a pain in the but to adjust, but then again I think I would rather have that problem then be stuck.
To summarise, the benefits of jet fins (the preferred technical fin) are?
- They are negatively buoyant which is ideal for dry suit divers
- They do not have plastic clips so you avoid the situation where you can’t dive cos you have broken a piece of plastic
- The entire strap is designed to present a smooth surface and so avoid catching on anything
- The blade is firm allowing for better speed and less silting using technical finning techniques
The cons are :
- They are heavy and so more work than something like a split fin
- They come in black, black or black (admittedly not a serious con, but still)
- They do not have an easy to release clip which means getting into them and out of them when dressed in layer on layer of warm stuff is a problem, especially in a dry suit that does not have a telescopic torso.
So what are the alternatives ? My favorite fins are the SCUBAPRO SPLIT FINS. Firstly, they are light so you do not have the feeling that your feet have suddenly turned to lead. Secondly, on a straight scissor kick they are fast and effortless (I was seriously surprised when I tried mine out…spent my first dive checking that the fins were still there and being amazed at the turn of speed I could muster). Oh, and they come in something other than black (a nice neon green for starters). They are modeled on nature (specifically the tail fin of a Humpback whale) which is capable of shifting tons of water with a single stroke. And they are fast being designed for speed and minimal effort (features inclide a patented split fin propulsion system; patented drag reducing vents that reduce drag on both the up and down strokes and an extended sole plate to increase leverage and power output). Simply put a split fin is designed to produce more forward motion with less effort using a scissor kick, which is where the problem comes in.
The last finning technique I find myself using in a cave is the scissor kick because whilst it generates speed, it also has too much downward force and so it generates silt and silt is every technical divers demon. I have been using my split fins for a while and so manage to avoid silt… but at the cost of speed which is an issue, especially when you want to do a long exploration and are on a time line. The problem with the split fin is that the lightness and effortlessness comes from a blade that is just too flexible. This flexibility makes for comfort but makes it more work to move heavy bulky gear through the water.
In a nutshell, split fins are :
- Lighter with a more flexible blade which is a negative for technical diving as it makes floating feet worse and means more silt and less speed when navigating heavy kit around narrow tunnels.
- They do have easy release clips (which I am still a fan of) and do come in a variety of colours (yes, colour is important but perhaps not that important J)
The sad thing is that whilst I love my split fins I have moved back to the traditional jet fin simply because of their superior performance with regard to anti-silting and speed. Do I like them ? Nope, not much… yet! But I am sure after a couple of months I will no longer remember the light and pleasant split fins and instead be comfortable with what feels like two small planks that remarkably have the ability (against all appearances) to enable me to turn on a tickey and dive in a silt free world. The good news is that Scubapro makes both, so at least I have that.
Monday, July 21, 2008
Here is the article Nuno wrote:
Diving history has been made in Lago Maggiore, Northern Italy. On 10th May 2008 three divers, Pim van der Horst, Mario Marconi and Alessandro Scuotto did “The Deepest Wreck Dive”. They dived the wreck of the “Milano” located at a depth of –236 meters of fresh water, the divers used the “Ouroboros” closed circuit rebreather. The logistic preparations for this dive were both comprehensive and impressive. The support by the Italian diving community was total and it included both sport divers as well emergency diving personnel. The dive was planned by Marco Braga, Andrea Cortesi and Fabio Manganelli with the assistance of many other volunteers. An ROV, positioned on the wreck of the “Milano” at –236 mfw, provided a visual beacon for the divers (with its lights), it also monitored the safe arrival of the divers at depth and established visual proof that they had been there. The most critical infrastructure that was available for this dive was a diving bell (fitted with a hot water and surface gas supply as well as visual and audio communication). The diving bell allowed the divers to decompress in comfort for the last four hours of the seven-hour epic dive. The dive went off without incident and as planned until Pim arrived back at –120 meters at which point his dry suit flooded (this was a problem because the water temperature is around 4 to 6 degrees centigrade), he managed to survive and was assisted into the bell at –21 meters by his support diver Remko van de Peppel, at that stage he was very weak and unable to do so on his own. At –100 meters, on the way up Alex started to feel dizzy and had to bail out to open circuit due to vomiting, with the assistance of his support divers and Mario he too was able to reach the safety of the diving bell. Mario’s dive went on without incident and he communicated with the surface from the diving bell, on the condition of his dive buddies. He also assisted them when possible because they were both vomiting frequently while decompressing in the safety of the bell. Upon surfacing Alex was evacuated for further treatment in the Recompression Chamber while Pim whose condition had improved remained under observation. Mario, after a medical examination, required no further attention except for a good night’s sleep. The whole team can be congratulated on doing a very difficult record dive and on recovering from a number of potentially fatal emergencies. I had the pleasure of being a witness to a well-executed dive instead of being one of the divers doing the record, for a change(236m).
Wednesday, July 16, 2008
Decompression sickness or DCS is the body’s reaction to bubbles. These bubbles can lodge anywhere in your system (brain, spine, lungs, heart, muscles) and tend to be made of either nitrogen or helium (this obviously depends on what you are breathing when you are diving, nitrogen and or helium). The gases that you breathe are transported from your lungs to all areas of your body (tissue) in the blood along with the oxygen you need to survive. The deeper you go, the more ‘thirsty’ your tissues are for these gases, so the faster they absorb them (a process called in-gassing). This absorption process occurs until the amount of gas outside the tissue is exactly the same as inside (as measured by the partial pressure of the gas). When you change depth and ascend the tissue suddenly has more gas than blood and so releases the gas, a process called out gassing. This is the simplest picture I can paint…and so has its own set of inaccuracies, but you get the idea.
Not all tissues have the same reaction to an increase in the amount of gas available. Some are thirstier than others. When a tissue is greedy and absorbs gas fast it is called a fast tissues and when it takes its time to take on board the new gas, it is called a slow tissue. The speed at which tissues absorb gas is used to classify every tissue in the body. To make it easier tissues are further grouped together into compartments that behave in more or less the same way, absorbing and releasing gases at the same rate (Buehlmann created 16 compartments). The compartments are important for decompression programs as the maths then treats all tissues in that compartment as having the same absorption features.
When discussing tissues the phrase tension is often used (tissue tension) which is simply another way of saying the amount of gas (nitrogen or helium) that is absorbed by that tissue (or put yet another way, the gas pressure). The tables ensure that the tension of the gas in the tissue does not drastically exceed the outside tension. When it does.. bubbles result.
The amount of time it takes for a tissue to release (or outgas) its nitrogen or helium is referred to as that tissues half time. This is a standardised unit that measures the amount of time it takes for a tissue to halve its gas tension (halve the amount of gas it has absorbed).
There are a number of different factors that affect whether or not a tissues is fast or slow, these include the degree of blood flow to that tissue (perfusion), the amount of blood vessels within the tissue and so the distribution of the blood to a tissue and the solubility of the tissue (i.e. how easily it absorbs nitrogen and helium.) This means that areas that have a lot of blood vessels (good perfusion) tend to be faster tissues (lungs and abdominal organs). Slower tissues are normally fat and joints. Fat also holds onto nitrogen better (incidentally this is believed to be one of the reasons we are susceptible to narcosis, our neurons are sheathed in fat and fat likes nitrogen).
One common misconception is that as you ascend all your tissues will be outgassing. But not all the tissues find themselves in a situation where the pressure outside is less than the pressure inside… which means that they are in fact still ongassing (the tension of the tissue is less than the ambient pressure rather than greater than). This is more often the case on deeper dives and has been used as an argument AGAINST deep stops ( personally believe the value of the deep stop is to outgas your fast tissues effectively and stop these bubbling and causing problems at shallower levels. My philosophy is to let your slower tissues absorb, I will deal with them when I get to them J , i.e shallower)
A tissue is deemed to be saturated when the tension outside and inside is the same. The tissue is in a state of equilibrium, it neither takes up gas nor does it let it go. Supersaturation is when the tissues have more gas than outside (ambient pressure outside is less than the pressure of the tissue). Bubbles form when based on how high this supersaturation is (i.e. how great the pressure difference) and how long this state remains true. This is termed critical supersaturation.
Another element often referred to in tables is M-values. These are the maximum nitrogen tensions for a tissue after which bubbles form (or the supersaturation point). Fast tissues tolerate higher supersaturation rates than slower tissues and so have higher M-values.
Tables and decompression programs put all this together and use maths to calculate the times you need to stop to allow the tension in your tissues to subside (i.e. gas to be released into your blood, move to your lungs and then be breathed out). Most tables are parallel models in that they assume that all tissues are exposed to the effects of the gas at any one time…as opposed to serial models where each compartment reacts one after the other (which is obviously not true).
Simple right ? J
Tuesday, July 8, 2008
You may already be a fan of deep stops or you may be like a lot of divers, you have heard of them but have been diving successfully for years without them so don’t see why you need to change. Here is some food for thought (my sources for this blog are the NAUI Journal of Underwater Education, Vol 20, Issue 2 and the published journal on the “Effect of Varying Deep Stop Times and Shalo Stop Time on Precordial Bubbles” by Bennett, Marroni, Cronje, Cali-corleo, Leonardi Bonucelli, Balestra, Undersea and Hyperbaric Medicine 2007; 34(6).)
NAUI (as an example which is not meant to imply that other agencies do not already recommend this) had a recommended deep stop of 1 minute at a depth that is half that of the deepest depth reached on the dive. They have now changed that stop from 1 minute to 2 or 3 minutes ( the ideal being 2.5 minutes). This is based on the research by Bennett et al (for us more technically minded divers this ‘deep’ stop should be half the absolute depth and not half the actual depth…and yes, they really mean at least 2.5 minutes…read on)
What does the research say ? Well, it has already been proved that a deep 5 minute stop at 15 m (on a 25 meter dive) in addition to the typical 3 to 5 min shallow stop (6 m) significantly reduces the number of bubbles and fast tissue compartment gas tensions (this research also indicated that the optimal ascent rate from 25 m was 10 m/ minute). This led to a number of agencies introducing the 1 minute ‘deep’ stop. BUT, the new research indicates that 1 minute is too short and actually increases the bubbling rather then decreasing it. Dives with 2.5 minute deeps stops showed the highest bubble reduction. Interestingly the research also found that if you have a deep stop, you could drastically reduce the time you spent shallow without changing the bubbling.
Some underlying theory - most decompression computer algorithms and dive tables are based on the original ideas of Haldane or Hill. Haldane modelled gas uptake and elimination on 5 tissue compartments that were either fast or slow to uptake/ eliminate gas (the compartments are virtual entities into which the various parts of the body are assigned a group, for example, brain tissue and nerves are fast tissues, fat is a slow tissue…I will blog on the basics of decompression next week).
Buelmann increased the number of tissue compartments to 16 / 18 creating an algorithm that is perhaps more accurate and safer as a result. Most models are based on the common premise that as long as none of these compartments become supersaturated beyond a certain critical threshold, decompression sickness (DCS) is avoided. Haldane also (and critically) introduced the concept that it is as safe to come from 6ATA to 3ATA as it is to come from 4ATA to 2ATA, or a 2:1 ratio of absolute depth. This ratio of one half the absolute depth has been modified over the past decades and now ranges from 4 to 1 for fast tissues to less than 2 to 1 for slow tissues. Interestingly though, most tables adopted Hills approach of a linear ascent of 10m/ min with a safety stop at 3 to 5 meters. This meant that the concept of staged decompression at one half the absolute depth was eliminated… and so were the positive effects there-of. In essence this is what Bennett et al are doing, re-introducing a stop at one half your absolute depth. Their research indicates that such a deep stop (for their 25 meter dive) often completely eliminated type 3 and 4 bubbles (bubbles were graded as follows 0 (none), 0.5 (sporadic), 1 (15 bubbles over 1 minute with bubble showers), 2 (30 bubbles), 2.5 (>30 bubbles with showers), 3 (virtually continuous bubbling), 3.5 (continuous bubbling) and 4 (continuous bubbling with continuous showers).
What did they find across their various profiles ?
- After a 2.5 min deep stop, decreasing the shallow stop time from 5 min to 1 min had no significant difference to bubbling. They are do not come out and quite say it, but the evidence seems to indicate that the safety stop at 5 meters can be seriously reduced to as little as 1 minute although they still recommend it for recreational diving to prevent pulmonary barotrauma.
- Without a deep stop increasing the shallow stop time did not give you the same effect as a profile with a deep stop. So basically, without the deep stop you had significant bubbling and nothing you do changes that. This was supported when they increased the shallow stop to 10 minutes (from 5 ) with only a slight reduction in bubbling being reported
- If a deep stop is used, any times less than 2.5 minutes ACTUALLY INCREASES YOUR BUBBLING as compared to not having the deep stop at all. So basically either do not do the deep stop or do it properly spending at least 2.5 minutes, otherwise you are making it worse.
I find this research quite interesting as deep stops have always been part of my profile. In fact, I remember quite clearly asking Dr Cronje what advice he had to prevent decompression and him stating “prevent bubbles from forming” (well his actual answer was do not do the dive J ), which is what this research seems to indicate.
If you want to stop bubbling you have to stop it occurring, which is normally deep in your ascent. Staying shallow is there to remove bubbles that have already formed.
Dives that produce bubbles tend to produce DCS!
Wednesday, July 2, 2008
Here in South Africa the diving dry suit is more the exception than the norm. Well, for most divers. For those of us diving caves (or Cape Town or long decompression) a dry suit is a must. With the slow adoption of technical diving more and more divers are starting to move towards dry suits. The question is which one ?
For those of you who are reading who are not quite sure what a dry suit is… simply put it is sealed suit that prevents nasty cold water from ever reaching/ touching your skin (well ok, not your hands and your head, although you can get dry gloves and hoods but that is a bit of overkill in Africa). It does this through the use of seals that prevent water from entering the suit at your neck and wrists.
There are many brands of dry suit available to a diver, but only these tend to fall within two main types, a shell or membrane suit or a neoprene suit. Each 'type' has its own set of pro’s and cons, not the least of which is price (indeed price is often the most important factor when selecting a suit).
MEMBRANE DRY SUITS
Shell suits are so called because they are made of a thin, strong and durable material that creates a shell around the diver. This resembles a hard wearing membrane and is made up of layers. For our use the only way to go is a tri-laminate membrane suit as the bi-laminate is just too thin and prone to breaking (a membrane dry suit is worthless if it leaks). As the suit is a thin'ish membrane there is little insularion (unlike a wet suit). The intention is too keep the water out so with a membrane suit inners must be worne to provide warmth. Without the inner (think portable sleeping bag) diving in cold water is akin to standing in a gale with a dry mac on…i.e. cold!
There are a number of advantages to a membrane suit :
- They are cheaper than neoprene (especially crushed neoprene)
- They do not change their thermal insulation and buoyancy properties with depth (neoprene compresses and so becomes less effective)
- They are versatile as you can change your inners (and so your warmth factor), moving from a thin inner (or even just a track suit) to something hectic and more appropriate for arctic conditions.
They do however have disadvantages:
- They are not as flexible as their neoprene cousins, so if you are dressed up for warmth reaching fins can be a problem
- They have little to no thermal insulation properties so if your suit floods, you stand the chance of freezing unless you have some hectic inners or a heating system (they do exist)
NEOPRENE DRY SUITS
The neoprene counterpart comes in two varieties, normal neoprene and of course the deluxe and ultimate... crushed neoprene. The big difference with a neoprene dry suit is that you tend to use them without inners (unless you are using crushed neoprene of which the DUI is the only choice).
Advantages of neoprene:
- They have in built thermal insulation like a wet suit so if you have a loose fitting one (not normally the case, they normally fit tight like a wet suit) you can add warm inners and so create the ultimate suit for long, cold stays
- Because they are neoprene, if you flood your suit you stand a better chance of heating the water up and surviving
- They are more flexible than a membrane with more give
- Unfortunately unless you are diving crushed neoprene, you lose a good part of you insulation properties at depth thanks to compression and you end up with buoyancy issues
- Price! Crushed neoprene suits will make you weep and even normal neoprene is more expensive than a membrane
So which to choose ? I did my world record using a Scubapro membrane suit. Nuno Gomes prefers neoprene because of the thermal insulating properties. I have now moved to a DUI crushed neoprene but the jury is still out. There was nothing wrong with my membrane and the only reason I moved to neoprene was because my next dive will be over 6 hours and I need extra warmth (read on for the paragraph on pee valves). Most of the divers we talk to make their choice based on price, which means membrane (especially if they need a custom fit).
Once you have chosen between membrane or neoprene you still have to choose from selections like;
- telescopic torso (a must as it gives you manoeuvrability, flexibility and comfort),
- where the dump valve goes shoulder or cuff (shoulder is better as it is out of the way and high up on the suit, on a cuff dump you have to spend your ascent with your hand above your ear….kinda inconvenient)
- and whether or not you want extra thigh pockets (yes, you do, they are damn handy)
Suits also come with back entry or shoulder/ front entry. To be honest, I still need help on the self donning shoulder entry suit but only with that last centimetre. Having said that, the self donning is still way easier to get into and out of than the standard and more common back entry which requires either a second person or some interesting antics as you try and ‘catch’ the zip tag and then pull it closed (or open) using a convenient protrusion (think cat scratching its back)
When it comes to a brand you have a wide choice, especially with the internet. Our recommendations are Otter or Scubapro (naturally) as these fit within our target price range (you do not want to know how much a DUI is these days). We find that we sell more Otter's simply because you can get a custom fit at a really reasonable price (and to my eternal regret, Scubapro does not make custom fit suits). Why is custom fit so important ? Well most divers actually battle to fit into the standard off the shelf cuts, especially if you are female and buying a male cut (which is often the case). Custom fit also means you do not have to spend your life with a size 8 or 10 boot when you feet are a size 6 (based on the off the shelf suit you had to choose to get your length and girth to fit).
Another question that is hotly debated is when to purchase a dry suit ? Normally divers leave the dry suit to last, well after they have bought their Liquivisions or VR3's. Which I find odd. You can always (and normally do) plan your dive on paper so a helium computer is a luxury BUT you can not easily unfreeze yourself doing those 2 to 4 hour dives in cave cold water. From a pure risk management view point maintaining your body temperature should be one of your primary and critical factors that you are managing. Being cold is just way more of a risk than having a snazzy helium computer that means you can cut corners and not plan on paper before a dive. My advice is always to get the suit before the computer (they cost more or less the same).
The final topic that does need to be discussed (and one that I am not going to blog about, I will leave that to Gerhard) is that of pee valves. This is a conversation that I really do not want to know more about and is exclusively an option for the male dry suit diver and yes, I am jealous. When I do a deep dive I have to wear incontinent nappies which last like twenty minutes after which I am wet and cold . The guys fit their condom catheters and spend a blissful 4 hours warm and more importantly dry.
Would I ever go back to diving wet ? No way! I have only ever been too warm in a dry suit once and compared to being almost permanently cold and unable to warm up after repetitive dives I think the warmth of kitting up in mid summer is a small price to pay. Admitedly sea dives take some getting used to these days as it is harder to get back into the boat because I have a power inflator on my chest that catches me as I try and get in but then again, sea dives are not really on my agenda much so I guess I can live with the inconvenience. If you are a technical diver my only question to you is, why are you not diving dry yet ?
Wednesday, June 25, 2008
This sense of uncertainty extends to situations where a buddy pushes his limits to the point of being physically affected. He gets out the water looking a tad pale and then starts to throw up (discretely). What do you do ? There is a good chance that the buddy is not going to take kindly to being driven to the closest hospital just because he is throwing up. Do you leave him ? After all he is a grown up! Where does individual responsibility end ? Where do you draw your own personal line ?
I understand the dilemma having had a similar experience with a very close friend. He was doing support at 100 meters when i was doing one of my deep build ups (140 m if I remember correctly). By the time I was out the water he was already back at camp with a migraine and throwing up.
This raised alarm bells for me. Yes, he was prone to migraines, but one of the fundamental guidelines for making decisions on a diving trip is that all physical symptoms are first attributed to diving and a possible bend, then to normal day to day niggles. No-one wants to make something big out of something small, so our tendency as individuals is to mind our own business and do nothing. By 6 in the evening my buddy was worse and still throwing up. He was also belligerent and refusing help. We phoned Dan!
They recommended we take him to the closest hospital. We were loathe to do that, after all it was probably just a migraine and hospital sounded like over kill. We would also have to force our friend to go. By 8pm the situation had not changed and as a group we realized that we would rather look foolish on Sunday then have a good friend seriously and permanently injured. We dragged him kicking and screaming to the hospital. They were also unsure but sent him off to the chamber just I case and a good thing to, because it took a chamber treatment to recover his memory and get him better. We are still not sure what exactly happened. It was probably a cerebral bend which meant if we had done nothing our friend would have been permanently impaired.
What did I learn from this ? Two things, firstly you look more foolish when you do not react as if it is serious and secondly, I need to be able to live with myself and that I do not want to live with the guilt of having done nothing and seeing some-one die or become crippled. Most of the things I regret in diving involve not speaking up. You may not change anything by speaking up, but you at least offer the individual the opportunity to make a different choice.
This means that I am vocal about my expectations of a buddy because it is not only about them, I have to live with what happens as well. We agree before hand how we expect each other to behave. I expect my buddies to tell me if they are concerned about decisions I am or am not making. I expect them to keep an eye on me after a dive because I know that if I am not feeling well I probably will not mention anything and it will probably take someone making something of it before I go to hospital. I expect my buddy to have high standards and to care about his life and mine!
So next time you are on a trip and you see yoru buddy acting in a way that will endanger his life or your own, speak up! If you are still uncomfortable do not do the dive (or at least not with him). Keep an eye on your buddy after a dive and check up on him. If he seems to be ill call him on it. Phone DAN and ask for their advice.
Remember, life is too short for regrets and trust me, when something goes wrong you will regret doing nothing and ‘going along’ to keep the peace. I would rather have a buddy who is cross with me, than a dead or impaired one.