Scuba & Nitrox Glossary: D
Nitrox and breathing-gas terminology is prioritized first. General scuba terms follow below. Definitions are educational summaries and do not replace formal training, manufacturer instructions, or an operational dive plan.
Nitrox & Gas Terms — D
- Dalton’s Law
- The total pressure of a gas mixture equals the sum of the partial pressures of its component gases.
- Decompression Gas
- A gas carried or supplied for decompression stops, often with a higher oxygen fraction than bottom gas.
- Depth Limit
- The shallowest applicable limit created by certification, environment, gas MOD, equipment, or dive plan.
- Dive-Computer Gas Setting
- The oxygen fraction and related parameters programmed into a computer to match the analyzed gas.
- DNAx
- A historical term for denitrogenated-air Nitrox produced by removing nitrogen from air.
- Decanting Oxygen
- Transferring oxygen from a supply cylinder to another cylinder by pressure equalization.
- Dedicated Nitrox Cylinder
- A cylinder identified and maintained for enriched-air service under applicable rules.
- Decompression Gas Switch
- The planned change to a richer gas during ascent at or shallower than its MOD.
- Depth-Adjusted PPO2
- Oxygen partial pressure calculated for the current absolute pressure and mix.
- Diluent Flush
- A rebreather procedure that replaces loop gas with diluent for verification or control.
General Scuba Terms — D
- Decompression
- The reduction of ambient pressure during ascent and the process of managing dissolved inert gas.
- Decompression Ceiling
- The shallowest depth to which a diver may ascend without violating the decompression model.
- Decompression Sickness (DCS)
- Injury associated with inert-gas bubbles forming in tissues or blood after pressure reduction.
- Decompression Stop
- A required pause at depth during ascent.
- Delayed Surface Marker Buoy (DSMB)
- An inflatable marker deployed underwater to show a diver’s position or provide an ascent reference.
- Depth Gauge
- An instrument that displays depth.
- Dive Flag
- A locally regulated flag used to indicate divers in the water.
- Dive Log
- A record of dive conditions, profile, gas, equipment, and observations.
- Delayed Surface Marker Buoy
- An inflatable marker deployed from depth to show a diver's position.
- Descent Reference
- A line, wall, slope, or visual cue used to control descent.
- Dive Briefing
- A pre-dive review of site, plan, hazards, signals, and emergency actions.
- Dive Platform
- A vessel or shore structure used for diver entry and exit.
- Dynamic Buoyancy
- Buoyancy changes experienced while moving through different depths.