Kevrumbo
Banned
- Messages
- 5,659
- Reaction score
- 1,361
- # of dives
- 1000 - 2499
Deep Air/Dark Narc encounter to 80m on Oil Rig Eureka here in offshore SoCal 2yrs ago, in 12deg C water temp depth at the time. Used double AL80 11L manifolded cylinders, an AL80 11L tank of Oxygen, a drysuit for exposure & redundant buoyancy, and a DPV Scooter.
Planned dive was a quick powered scooter descent to 90m for a few minutes, and then multi-level profile up with most of the time spent at 18m, with O2 deco at 6m as needed. Total Dive Time was 50min, with deco obligation cleared before 12m (per Petrel Computer on 30/85 GF), but I did a few minutes on O2 at 6m anyway for a cleaner inert N2 purge.
With the scooter off and stowed, all it took was three forceful & physically exerting frog kicks into the stiff current at 80m depth, and I was instantly overcome with a narcotic CO2 hit: Hyperventilation & difficulty breathing the regulator, high density & flow viscosity of the Air mix & resulting Hypercapnia came on immediately. In the dim ambient light, the only thing I was able to perceive was my Dive Computer flashing an extreme PPO2 Warning prompt of 1.9, and it took a few minutes focused concentration not to panic, just to hang onto a support beam and try to relax & regain a nominal breathing rate & clear head before starting the ascent using the scooter. (Note: Elevated CO2 also increases the likelihood of hyperoxic seizures.) The point is that a Deep Air bounce dive like above can be treacherous enough even if planned and prepared as a technical dive on double tanks with plenty of gas supply margin to recover at depth from Hypercapnia . . .It would be dangerous and near fatal tragedy to make this mistake on a Single Tank!
Not at all pleasant and I don't want to do that again. . .
Planned dive was a quick powered scooter descent to 90m for a few minutes, and then multi-level profile up with most of the time spent at 18m, with O2 deco at 6m as needed. Total Dive Time was 50min, with deco obligation cleared before 12m (per Petrel Computer on 30/85 GF), but I did a few minutes on O2 at 6m anyway for a cleaner inert N2 purge.
With the scooter off and stowed, all it took was three forceful & physically exerting frog kicks into the stiff current at 80m depth, and I was instantly overcome with a narcotic CO2 hit: Hyperventilation & difficulty breathing the regulator, high density & flow viscosity of the Air mix & resulting Hypercapnia came on immediately. In the dim ambient light, the only thing I was able to perceive was my Dive Computer flashing an extreme PPO2 Warning prompt of 1.9, and it took a few minutes focused concentration not to panic, just to hang onto a support beam and try to relax & regain a nominal breathing rate & clear head before starting the ascent using the scooter. (Note: Elevated CO2 also increases the likelihood of hyperoxic seizures.) The point is that a Deep Air bounce dive like above can be treacherous enough even if planned and prepared as a technical dive on double tanks with plenty of gas supply margin to recover at depth from Hypercapnia . . .It would be dangerous and near fatal tragedy to make this mistake on a Single Tank!
Not at all pleasant and I don't want to do that again. . .
