P2 Hollis Prism 2 Pre-dive workspace

CCR refresher

In-water cheat sheet

Three skills to keep wired in muscle memory. Not a substitute for training — print this, take it on the boat, drill it dry.

Skill 01

Diluent flush

Do it when

  1. PPO2 reads high and the solenoid will not stop adding O2.
  2. PPO2 reads low and you can't explain why.
  3. CO2 build-up: working harder than the dive justifies, breathing fast, hot, mild headache.
  4. You took a hit of an unknown gas (water, contaminated loop).
  5. After cell calibration to validate sensor response.

Steps

  1. Confirm PPO2 of your diluent is breathable at this depth.
  2. Open OPV one click so excess gas can vent.
  3. Tightly squeeze inhale counterlung to flatten it.
  4. Exhale forcefully into the loop while pressing the ADV (or manual diluent add).
  5. Re-check O2 sensors; repeat once if reading is still suspect.

Skill 02

Bailout to open circuit

Switch when

  1. Sensors disagree by more than 0.1 PPO2 and you can't resolve it.
  2. PPO2 confirmed high or low after a diluent flush.
  3. You suspect CO2 break-through (scrubber failure).
  4. You hear or feel water in the loop. Caustic = burning taste in mouth.
  5. The handset reports a manual-override condition or fails to display.
  6. Your buddy is in trouble and you need both hands available.
  7. Any time the dive feels wrong and you can't pinpoint why.
Bail out first. Sort it out second. Open circuit then ascend. SCR is not a bailout for most CCR divers.

Skill 03

ID10T test

Read it as idiot. Last 30-second sweep before stride.

  1. Mouthpiece DSV closed, in position.
  2. Both cylinders open, valves cracked per dive plan.
  3. Computer on, gas profile loaded, decompression-mode confirmed.
  4. Bailout routed where you can reach it with the OFF hand.
  5. Wing inflated, drysuit inflated, both have a path to vent.
  6. Mask clean, defogged, on. Weights distributed and locked.
  7. Buddy check exchanged. They know your bailout plan.
  8. Loop in, hand on BOV, ready to switch.