My biggest fear ....

[SM Diver]

I'll tell you my biggest fear having just completed the requirements for my PADI c-card. My biggest fear is not being able to dump air from my BCD, causing a sudden acceleration to surface.

Two things have happened that have caused this concern. First, a friend with many dives under his belt, told me of the two times he has had a sudden, uncontrolled ascent from depth, the last one resulting in DCI. He ascended, air expanded, and it set off the chain of events. Why he couldn't dump air, I don't know.

The second thing happened on my last check out dive. I was wearing a brand new BCD, and my dump valve would not work at depth. In fact, neither the dump valve or thumb valve worked. Fortunately, I was able to hang-on to a rock, get my instructors attention, and let him know I was having a problem. After he repositioned it, it was fine. Had I been alone, I am not sure. I guess I could have made myself upside-down and grabbed the lower rip-cord.

So, my question is: How many of you have rapidly ascented to surface due to inability to dump air? What drills can I work on for this emergency?

By the way, this concern is not affecting my new love for this activity. I am officially hooked - BIG TIME!


Thanks.

Scott
Tampa

 

[nickjb]

There is a current discussion about this here:

http://www.scubaboard.com/showthread.php?s=&threadid=11166

It should answer most of you questions

 

[art.chick]

I HAVE had the inflator hose stuck on several times. Yes, once you start ascending, you have to act fast, otherwise you get closer & closer to the shallow waters & accelerate. As your buoyancy improves, you will notice faster when you are a bit off balance. If the dump valves are faulty, you need to get them serviced, but it could be that your BC just traps air where it is inaccessible. My old BC did that all the time. I really did have to be turned upside down & shaken out!

Last summer, I got some crud in my inflator hose & did not have the knowledge to fix it myself. There was a month-long back-up in the repair dept.s of all LDSs. I had a long class every weekend all summer, so my instructor just disconnected the inflator hose & said, "Orally inflate. You will be fine." All summer, I had no automatic inflator. I WAS fine. I realized how often I was adding air when I really needed to just relax & breathe better.

I do not know how responsible it would be to tell an OW student to just disconnect their hose, but in an emergency (ie, you are at 60' & it keeps getting stuck on) it could save the dive. Lots of newer divers I assist with overuse the darn inflator & get into a whole lot more trouble than they would have if they could not puff up like blowfish at an instant. If you are not overweighted, you don't really need to add air at moderate depths. Your inflator is not likely to get stuck on if it is not being used in the first place.

 

[nickjb]

Your last point is very good. On a normal dive profile you should add air before entering the water. Dump air to sink, add a little air at the bottom from then on you should be dumping air to stay neutral as you ascend

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[chrispete]

I've gotten into the habit of doing manual inflation underwater regardless - I've very rarely used my power inflator since OW. I would probably not do this under conditions that I wasn't very comfortable with, but I feel ok with it (plus the bonus of saving a little air to boot.)

On your dump valves, I may be a bit anal, but after every dive I break down all of the exhaust valves on my BC, including the valve on the power inflator hose, and clean them out completely - it helps me to be comfortable with the fact that I know that they are clean and in good working order with no large debris in them(they're very simple little things and that's about the only thing that I can see that would cause a dump failure save for the string breaking off) and to make sure that no leaks will occur next time I'm out.

One thing you may want to do for your comfort level would be to keep in mind that on most of the BC's I've seen out and about, the power inflator hose is also a dump valve - if you are wrestling with a runaway inflation, don't go digging for your right shoulder dump, give the inflator hose a good yank and that'll let you keep your eyes and hands on the part of your setup that's giving you the trouble. Art.chick also makes a good point about keeping the location of the air in your BC in mind, you can yank a dump valve all day long, but if the pocket of air is trapped on the other end of the bladder, it's not going to do much of any good.

Keep at it, I don't have many dives under my belt, but those nagging fears do go away (rather quickly) after you've been underwater for a while and come to know and trust your skills and equipment!

 

[SM Diver]

I know that it wasn't a maintenance issue with me, as the BCD was purchased brand new from the LDS doing the course. It was the first dive it had been used. It worked great, except fot that one incident. Maybe it was just an issue of not having used that BC before, and not knowing its tendancies.

I have decided to undertake the following, in order to give me maximum confidence. I am going to hire today a private instructor that comes highly recommended in this area. I am going to dive with him several times for a month, and work almost exclusively on drills. I want him to disconnect my hose, over inflate my BCD, and throw all kinds of hazards at me so that I can practice a calm response. IMHO, the certification class probably give you the knowledge you need to dive in ideal situations, but I would bet that almost no new divers are ready for an emergency. This may be overkill on my part, but the drills will be a lot of fun, and may save my life someday.

Scott

 

[MikeS]

One of the things I learned in AOW class was to maintain slightly negative buoyancy during ascent. This means that you must use your fins to swim up. To stop going up, simply stop swimming up. Release air as you rise to maintain slightly negative buoyancy. Of course you want to achieve neutral buoyancy for the safety stop. To go up from the safety stop I actually dump some air to get slightly negative before starting up.

I found that if I get positively buoyant and start to rise it’s very difficult to dump air fast enough to slow down without becoming a yoyo. The problem is compounded by the anxiety caused by the lack of buoyancy control, which at least in my case causes me to loose control of breathing which makes buoyancy control even more difficult. I’m not sure if this is the case for everyone but I’m much better at smoothly stopping a descent than stopping an ascent. I suspect this is because in a head up orientation you can use your fins to stop your descent.

If possible I like to ascend next to a line. It’s very comforting knowing that you can reach out and grab it if you start to loose control. But I give myself points for not having to touch it. From what I’ve learned so far maintaining buoyancy during an ascent is half technique and half psychological. If you feel in control it’s easy control your breathing and stay in control.

Hope this helps,
Mike

 

[Uncle Pug]

Sorry to disagree with you Mike:

I would suggest that you practice proper ascents in 15'~20' of water. Properly weighted and neutral at the bottom with a full tank and some air in the BC to compensate for the weight of the air in the tank. You should be neutral with half a lung full... this is important.

Keep yourself horizontal (this will add drag and slow your ascent making it easier to control... hopefully your BC will support dumping in this position.... if not there is the solution....PM me.)

Keeping yourself horizontal take a full breath and you should start to rise slowly off the bottom. As you do air will expand in your BC and you will start to rise a little faster... at this point dump enough air to slow yourself while exhaling... if you start to sink then inhale... if you are still sinking you dumped too much air from the BC... add a little... and try again. In the initial stage of learning you will yo-yo up and down... but if you keep trying you will get it.

Practicing in shallow water will be safer for one, give you confidence where control is the most important (20' to surface) and this is also where the air expands the most so it will be more difficult. If you can do this in 15' of water you can do it anywhere.

Several things to consider.
1) Shoot for very slow ascent rates... first try to hit 30 fpm then 20 fpm and 10 fpm and finally see if you can do a 5 fpm ascent.
2) Keep horizontal as much as possible... go vertical and you will shoot to the surface.
3) Remain motionless as much as possible... no finning and no hand waggling... this takes discipline.

The idea of a slow ascent is to minimize bubble formation...
The idea of no movement is to minimize bubble formation...
Muscle activity on ascent tends to maximize bubble formation...
Remember the soda can illustration from OW class?
Shaking the can makes things worse.
So both shooting up and finning up are bad practice.

Btw this execise will get a little more interesting as it progresses.... in that your tank will become less negative as you use up air... properly weighted means the ability to remain neutral with only 500 psi in the tank while at 10' (some say 0')

 

[MikeS]

UP,

The idea of ascending while horizontal makes a lot of sense if not for the fact that as you pointed out, it’s difficult if not impossible to dump air from my BC while horizontal. Per your suggestion I will PM you for “the” solution but is this not something everyone would benifit from.

Mike

 

[SM Diver]

Mike, I know where you're coming from on having a line to follow-up. There is a grotto owned by a LDS that goes down to 130. It has platforms at 22, 44, etc.. It is really nice because the corners of the platforms are allattched to cables, hooked to buoys at the surface.

I am going to start spearfishing and taking photos out in the Gulf, within the next couple of weeks. I am going to use my downrigger to lower a cable to the bottom, and follow it up. I guess the anchor line would do the same thing, but the downrigger will bring me right next to the dive ladder.

Another idea is to use a dive buoy that I could throw out when I see the reef on the fishfinder, with the buoy being attached to a weight at the bottom. That would serve the dual purpose of dropping me down over the fish, and giving me a line to follow-up. Anyone ever jerry-rigged a line to the bottom like this. or using a different system?

Scott