luvx77x8o4
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Can someone help explain what a NO decompression dive is and what a decompression dive is. Thanks. 
decompression dive
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Ben_ca
Contributor
No Deco is one where you can ascend directly to the surface without a mandatory decompression stop
A Deco dive you must make your stops
A Deco dive you must make your stops
In the world of recreational/sport scuba diving the certf. agencies pretty much set a standard of No Stop (non deco) diving at 130ft,,,,meaning in theory you may decend and accend within safe speed, and in theory never stop as in a 'Safety Stop' say at 15ft. for 3 minutes upon your accent......of course as a wise diver you should always make these Safety Stops assuming you have the appropriate supply of remaining gas,,,,you are 'off gassing' nitrogen from your body system, reducing the chances of a DCS hit. In sport diving the common practice is the make a min. Safety Stop at around 15ft. for 3 minutes....on deeper dives say at 100ft. or deeper it is wish to make an additional Safety Stop at approx. have your max. depth for a minute or two prior to continueing your slow accent. Decompression diving is done outside the sport depths and general bottom times,,,,this is were the deco stops become mandatory for a safe accent to the surface.
Don Burke
Contributor
Strictly speaking, every dive involves decompression.luvx77x8o4:Can someone help explain what a NO decompression dive is and what a decompression dive is. Thanks.
In common usage, a "no decompression dive" is one where an ascent rate of 60 feet per minute provides enough decompression to avoid problems.
In common usage, a "decompression dive" is one where the ascent above would not provide enough decompression to avoid problems, in which case stops at various depths are normally made to provide enough time to offgass. It would be possible to ascend slowly enough to provide for the offgassing, although I have never seen that done.
I have stopped using the terms "no decompression dive" and "decompression dive".
I now use the terms "no stop dive" and "mandatory stop dive" to avoid confusion.
BigWhiteSquare
Contributor
Hmm. In one of your previous posts you asked what a "c-card" is. Are you sure you've finished your training? I'm not trying to be critical, but these seem like very basic questions you're asking. Did your instructor not tell you these things?
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Trisha
Contributor
I am not a scuba instructor, nor do I play one on TV.
No decompression dive: A dive within the accepted limits of depth and time to minimize the effects of breathing compressed air at depth. Proper accent includes an ascent rate of 30 ft/minute (60 ft/minute below 60 feet) and a recommended safety stop of 3 to 5 minutes at 15 feet.
In theory, some say the decompression stop is an option, not a requirement if you stay well within the dive table limits. But no one is going to recommend you make a practice of skipping it, since among other things slowing down at around 20 to 30 feet helps prevent popping to the surface like a cork -- bad news all around!
Decompression dive: A dive exceeding the recommended limits of depth and/or time. Decompression stops are required at various depths/times to offgas nitrogen in the system and reduce the possibility of decompression sickness.
Which means you screwed up. Technical divers get training to do decompression diving, but then they have the extra tanks, exotic gases, the desire to trade extra time and greater depth for hours -- hours -- of decompression time. And some of them still get bent. Bummer.
Bottom line -- when you get your training, pay attention to the bit about decompression sickness and how the risks increase with greater depth, longer time, and rapid accents. Give your body enough time to remove the excess nitrogen, and you remove a large risk factor in diving.
Good luck and keep us posted.
No decompression dive: A dive within the accepted limits of depth and time to minimize the effects of breathing compressed air at depth. Proper accent includes an ascent rate of 30 ft/minute (60 ft/minute below 60 feet) and a recommended safety stop of 3 to 5 minutes at 15 feet.
In theory, some say the decompression stop is an option, not a requirement if you stay well within the dive table limits. But no one is going to recommend you make a practice of skipping it, since among other things slowing down at around 20 to 30 feet helps prevent popping to the surface like a cork -- bad news all around!
Decompression dive: A dive exceeding the recommended limits of depth and/or time. Decompression stops are required at various depths/times to offgas nitrogen in the system and reduce the possibility of decompression sickness.
Which means you screwed up. Technical divers get training to do decompression diving, but then they have the extra tanks, exotic gases, the desire to trade extra time and greater depth for hours -- hours -- of decompression time. And some of them still get bent. Bummer.
Bottom line -- when you get your training, pay attention to the bit about decompression sickness and how the risks increase with greater depth, longer time, and rapid accents. Give your body enough time to remove the excess nitrogen, and you remove a large risk factor in diving.
Good luck and keep us posted.
OP
luvx77x8o4
Guest
BigWhiteSquare:
Well in class they never used words like C-Card. I remember them saying something about a getting certified, but I couldnt put 2 and 2 together. Plus, Decompression, no decompression, recompression...is confusing. I was trained to always do safety stops, just in case...Then when I bought a computer, and read the manual...It started talking about the compressions and it confused the hell out of me.
All dives are decompression dives.
When you go under the water, the pressure on you increases -- you are "compressed". Nitrogen is forced into your bloodstream and your tissues.
When you come up, the pressure decreases -- you "decompress". Eventually the nitrogen tension in your tissues/blood is higher than in the gas you are breathing, and nitrogen starts to come out.
What we want is to have that loss of nitrogen occur at a slow enough rate that large, dangerous bubbles are not formed, either in the tissues or in the bloodstream. If you limit the amount of nitrogen you absorb, then you can keep that offgassing rate within safe limits while making controlled rate ascents without stopping. Note that, even if you dive within "no decompression" limits, a too-rapid rate of ascent from depth can result in problems.
At some product of depth and time, you will have absorbed enough nitrogen that it's going to take more time to come out safely than you will provide your body by a controlled ascent. At that point, it becomes necessary to create some pauses in the water, while still under some compression, to allow a slow and safe elimination of accumulated nitrogen. At this point, you are doing a "decompression" dive, with mandatory decompression stops. In a sense, you have just put yourself into an overhead environment, because it is not longer possible to solve problems safely by making a direct ascent to the surface. This is why people who do decompression diving also do a lot more training to solve problems underwater (and avoid them), because the risks just got a lot higher.
Hope that helps.
When you go under the water, the pressure on you increases -- you are "compressed". Nitrogen is forced into your bloodstream and your tissues.
When you come up, the pressure decreases -- you "decompress". Eventually the nitrogen tension in your tissues/blood is higher than in the gas you are breathing, and nitrogen starts to come out.
What we want is to have that loss of nitrogen occur at a slow enough rate that large, dangerous bubbles are not formed, either in the tissues or in the bloodstream. If you limit the amount of nitrogen you absorb, then you can keep that offgassing rate within safe limits while making controlled rate ascents without stopping. Note that, even if you dive within "no decompression" limits, a too-rapid rate of ascent from depth can result in problems.
At some product of depth and time, you will have absorbed enough nitrogen that it's going to take more time to come out safely than you will provide your body by a controlled ascent. At that point, it becomes necessary to create some pauses in the water, while still under some compression, to allow a slow and safe elimination of accumulated nitrogen. At this point, you are doing a "decompression" dive, with mandatory decompression stops. In a sense, you have just put yourself into an overhead environment, because it is not longer possible to solve problems safely by making a direct ascent to the surface. This is why people who do decompression diving also do a lot more training to solve problems underwater (and avoid them), because the risks just got a lot higher.
Hope that helps.
TSandM:
Thats something here at least a lot of people fail to appreciate. They assume if its a no stop dive even if they do their best ballistic missile impersonation they'll be ok as "no stops missed". There seems to be a general misconception at the lower level about ascent rates being that important. The message that all tables only work within specific rates of ascent isnt always getting through. Particulary guilty are some divers i see abroad who are terrified by the evil decompression (some agencies here imho dont help by making it sound out to be an evil fatal something to be avoided at all costs) dive their computers to within 1 minute of NDLs all the way and then have a bit of a rapid ascent in part or all of their dive.
Decompression is a soft not a hard ceiling meaning that absolute worst case scenario the surface is still there and help can be obtained. However depending on gas mix and amount of stops that soft ceiling becomes harder and harder until you reach a point where it'll be just as fatal as a rock above you.
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