Decompression

[Lord Northern]

Hello.
I heard a lot of stuff about deep diving and the need in staying in a decompression chamber for long time after each dive.
How exactly does it go? Do I even need it if I don't dive too deep? Is it dependent on the lenght of the dive? I'm much more interested in Distance Diving rather than Deep Diving so, I want to know if I'll need to care about decompression.



Thanks.

P.S Not yet a diver. Pretty soon going to a diving course.

 

[spectrum]

By definition recrerational diving requires no decompression events in a chamber or underwater. Observing established depth and dime limits will mean that you only need to make a slow return to the surface to end you dive safely.

Without getting into numbers that's how it works. It will all be covered in your openwater certification class. As long ar you don't go too deep your limiting factor will be your air supply, not your risk of decompression sickness.

Pete

 

[Lord Northern]

I see, and length? Does it play any role? I don't ask for numbers, but just any info on whether it matters how long I stay underwater, if I don't dive too deep?

 

[Fordan]

I see, and length? Does it play any role? I don't ask for numbers, but just any info on whether it matters how long I stay underwater, if I don't dive too deep?

Length does play a role... Basically, when your body is under additional pressure like it is underwater, it absorbs more nitrogen into your tissues. When that pressure is removed (like going back to the surface, or to a lesser extend by coming up to a shallower depth), the nitrogen comes out of your tissues. Nitrogen builds up faster the deeper you go, but even in shallow depths you'll build up nitrogen given enough time. If there's too much nitrogen in your tissues, or if you come up too quickly, that nitrogen will leave your tissues in the form of gas bubbles, which are dangerous.

When you take your dive class, you'll learn to use dive tables to figure out how deep/how long you can stay down safely.

 

[Lord Northern]

I see.
Thanks.

 

[kidspot]

As Fordon pointed out it's a matter of both depth and time - Your open water course will teach you how to use table/charts and/or dive computers to calculate the amount of time you can spend at each depth.

You will have a blast learning all this and lots more in your class - so I'd say "go for it" and have fun!

Aloha, Tim

P.S. Just to give you an idea - here's a copy of the Navy Dive Tables for a first dive of the day http://home.flash.net/~table/table/p0000149.htm ... while it shows depths down to 190ft, most agencies recommend staying shallower than 130ft.

 

[TSandM]

As has been written already, this will be covered in your OW course.

In short: Nitrogen is in the air we breathe, and as you go underwater, the pressure of nitrogen in the breathing gas increases. This causes more nitrogen to migrate into your body. That nitrogen has to come out as you ascend . . . And you have to ascend at some point!

The amount of nitrogen you absorb is a product of how deep you go and how long you stay. When you are very deep, you absorb a lot of nitrogen very quickly, and you can't stay there very long or you will have to spend a lot of time coming up slowly to allow the nitrogen to leave without making big bubbles that cause damage. When you are shallow, you are absorbing nitrogen, too, but more slowly. You can stay longer when you are shallow. There's some argument about whether there's a depth that is shallow enough that you could essentially stay there forever, but for practical purposes, it's hard to get into trouble above 30 feet (10m) because you'll run out of breathing gas before you absorb enough nitrogen to cause you issues.

No recreational dive is planned to end in a decompression chamber. That's a treatment that is used if someone ends up coming up faster than they can eliminate the nitrogen they've absorbed, and they end up with symptoms of decompression sickness. I understand that commercial diving is different, and sometimes they plan to exit the water and walk to the chamber, but we sport divers don't do that. Your OW class will spend a lot of time educating you on how to execute your dives so that you never see the inside of a chamber!

 

[Lord Northern]

Heh, I see. Basically, TSandMhttp://www.scubaboard.com/member.php?u=46629, you answered my question well: that's what I actually needed to know: if I don't plan to go deeper than 30 ft, then I can dive long enough without the decomression chamber. I was just dreaming to do an underwater trip of like 5 miles from one city to another once I master the skill - just a long dream of mine, and was checking to see if it'll even be possible.

Thanks, everybody.
It's kind of refreshing to find a place that's not full of 15 years old flooders but people who are willing to help and answer your question. Thanks again.

 

[wallacm]

Basically, you don't want to end up in a decompression chamber, they are expensive. It all depends on how deep you go and for how long. you can even be at 10 feet and have to decompress. Now when you talk to people that participate in decompression dives, they dive down to their depth for how ever long, and then they sit at 20 ft to decompress the nitrogen out of their bloodstream. Nitrogen in the bloodstream will be further discussed in your OW class. Now, if someone tries to cut off some of their time at 20 ft or they dont stop at all to decompress, they will get decompression sickness. then they will go to the deco chamber to do their decompression obligation at the expense of your wallet. So, in the end, NO dive (Recreational, technical, i'm guessing but commercial) is planned to go to the chamber, that is an extra cost that is not needed unless in an emergency.

Good luck and have fun in your class

 

[spectrum]

I was just dreaming to do an underwater trip of like 5 miles from one city to another once I master the skill - just a long dream of mine, and was checking to see if it'll even be possible.

5 miles would require some extreme measures for air supply, proulsion and exposure protection. Up to a mile on an 80 CF cylinder at something like 20 feet is well within the realm of posibility base on my experieince so far.

The liklelihood of needing a chamber ride is slight with good recreational diving you do not need to be alarmed by the costs. Most divers carry an isurance policy that covers these special risks.

Pete