Scuba & Nitrox Glossary: N
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 — N
- Nitrox
- A nitrogen-oxygen gas mixture; in diving, usually enriched air with more oxygen and less nitrogen than ordinary air.
- Nitrox-Compatible
- Equipment identified by its manufacturer or applicable standard as suitable for specified Nitrox service.
- Nitrox Fill Station
- A facility equipped and authorized to produce, analyze, document, and dispense Nitrox.
- Nitrox Tank Band
- A green-and-yellow or otherwise locally recognized cylinder marking indicating enriched-air service.
- NOAA Nitrox
- Historically standardized Nitrox mixtures used by NOAA, commonly associated with 32% and 36% oxygen.
- Normoxic Trimix
- A helium, nitrogen, and oxygen mix with enough oxygen to be breathable at or near the surface, depending on the chosen definition.
- Nitrox Bank
- A storage system containing premixed enriched air for cylinder filling.
- Nitrox-Compatible Regulator
- A regulator approved by its manufacturer for the intended oxygen exposure.
- Nitrox Fill Whip
- A rated hose assembly used to transfer enriched air during filling.
- Nitrox Logbook Entry
- A dive record that includes analyzed oxygen fraction and related settings.
- Normoxic Trimix Blend
- Trimix containing enough oxygen to be breathable at or near the surface.
General Scuba Terms — N
- Narcosis
- Impairment associated mainly with elevated inert-gas partial pressure at depth.
- Neutral Buoyancy
- A condition in which a diver neither rises nor sinks.
- Nitrogen
- The principal inert gas in air and a major factor in decompression and narcosis.
- No-Decompression Limit (NDL)
- The maximum modeled time at depth before mandatory decompression stops are indicated.
- No-Stop Dive
- A dive planned so direct ascent remains available within ascent-rate and optional safety-stop practices.
- Natural Navigation
- Using sun, current, depth, terrain, and other environmental cues to navigate.
- Negative Entry
- An entry made while negatively buoyant to descend immediately.
- Neutrally Buoyant
- A state in which a diver neither rises nor sinks without effort.
- No-Mask Swim
- A training exercise performed without a mask under instructor supervision.
- Nudibranch
- A colorful shell-less marine gastropod commonly observed by divers.