47 ms·

> They now use emergency tanks that carry 40 minutes of air rather than five. Glad to see the change, but why even carry a tank with 5 minutes of reserve? Migh

> They now use emergency tanks that carry 40 minutes of air rather than five. Glad to see the change, but why even carry a tank with 5 minutes of reserve? Might as well just plan on holding your breath in that case.

HeWhoLurksLate 7y ago
Well, it's better than nothing. That's enough to hold your breath 2-3 times, IIRC. That time means a lot.
- deleted 7y ago
  [deleted]
nradov 7y ago
The idea is that if there's a problem with the umbilical, 5 minutes should be enough time for a diver to get back to the bell where they have plenty of gas. But in this case the bell was dragged out of position.
ip26 7y ago
This is just idle observation, but when you ascend the air in your lungs expands and you are supposed to continuously exhale to prevent lung rupture. Supposedly if you start with a full pair of lungs, you can ascend pretty much from the bottom of the ocean on just one breath because of this. Also somewhat related, the deeper you go the less time your tank lasts. From what I remember, at 100m, a "5 minute tank" is probably similar in size to a standard scuba tank.
- idlewords 7y ago
  This is correct; scuba divers are trained to do a controlled emergency ascent while continuously exhaling, because your lungful of air at depth will last the whole way up, and the real risk is not running out of air, but embolism from overexpansion. The limiting factor in ascent (and therefore the reason for the recreational dive limit of 60 feet) is the risk of decompression sickness. If it weren't for that, a diver at arbitrary depth could ascend on a single breath.
  - nradov 7y ago
    Recreational dive limits are usually set at about 100 - 130ft (30 - 40m) depending on the training standards in use.
    - idlewords 7y ago
      The beginning certification level is 60 feet. You unlock the deeper limit after additional training, and it includes performing a three-minute "safety stop" at 5 meters. 60 feet is about as deep as you want to shoot to the surface from (and if memory serves the limit they give in training is 30 feet, or 2 atmospheres).
      - TheOtherHobbes 7y ago
        I've always been fascinated by how hard diving is. 60 ft seems like a completely trivial depth - about the length of four cars - but already there are non-trivial risks. And from there it rapidly becomes more dangerous and complicated and just plain hard to stay alive.
        nradov 7y ago
        It's not that hard. If you're interested then go ahead and sign up for a basic open water class. Most people can pass.
        m463 7y ago
        Lot easier than trying to go downwards with a snorkle.
  - Swifty 7y ago
    This is not entirely true, not all agencies teach a Controlled Emergency Swimming Ascent (CESA). From memory the only one that teaches this is PADI. Most don't as this is not a very effective or safe way of getting up once you get bellow a few M of water. Most agency's will teach you to do an Alternate Source assent where you come up breathing of your buddy's air source, as this allows you to come up at a safer and more controlled rate.

HeWhoLurksLate 7y ago

Well, it's better than nothing. That's enough to hold your breath 2-3 times, IIRC. That time means a lot.

deleted 7y ago
[deleted]

nradov 7y ago

The idea is that if there's a problem with the umbilical, 5 minutes should be enough time for a diver to get back to the bell where they have plenty of gas. But in this case the bell was dragged out of position.

ip26 7y ago

This is just idle observation, but when you ascend the air in your lungs expands and you are supposed to continuously exhale to prevent lung rupture. Supposedly if you start with a full pair of lungs, you can ascend pretty much from the bottom of the ocean on just one breath because of this. Also somewhat related, the deeper you go the less time your tank lasts. From what I remember, at 100m, a "5 minute tank" is probably similar in size to a standard scuba tank.

idlewords 7y ago
This is correct; scuba divers are trained to do a controlled emergency ascent while continuously exhaling, because your lungful of air at depth will last the whole way up, and the real risk is not running out of air, but embolism from overexpansion. The limiting factor in ascent (and therefore the reason for the recreational dive limit of 60 feet) is the risk of decompression sickness. If it weren't for that, a diver at arbitrary depth could ascend on a single breath.
- nradov 7y ago
  Recreational dive limits are usually set at about 100 - 130ft (30 - 40m) depending on the training standards in use.
  - idlewords 7y ago
    The beginning certification level is 60 feet. You unlock the deeper limit after additional training, and it includes performing a three-minute "safety stop" at 5 meters. 60 feet is about as deep as you want to shoot to the surface from (and if memory serves the limit they give in training is 30 feet, or 2 atmospheres).
    - TheOtherHobbes 7y ago
      I've always been fascinated by how hard diving is. 60 ft seems like a completely trivial depth - about the length of four cars - but already there are non-trivial risks. And from there it rapidly becomes more dangerous and complicated and just plain hard to stay alive.
      - nradov 7y ago
        It's not that hard. If you're interested then go ahead and sign up for a basic open water class. Most people can pass.
      - m463 7y ago
        Lot easier than trying to go downwards with a snorkle.
- Swifty 7y ago
  This is not entirely true, not all agencies teach a Controlled Emergency Swimming Ascent (CESA). From memory the only one that teaches this is PADI. Most don't as this is not a very effective or safe way of getting up once you get bellow a few M of water. Most agency's will teach you to do an Alternate Source assent where you come up breathing of your buddy's air source, as this allows you to come up at a safer and more controlled rate.