Scuba & Nitrox Glossary: I
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 — I
- Ideal Gas Law
- The relationship among pressure, volume, temperature, and quantity of gas; useful in gas planning and blending.
- Inert-Gas Fraction
- The portion of a breathing mixture that is not metabolically active, principally nitrogen and/or helium.
- Isobaric Counterdiffusion
- Simultaneous movement of different inert gases across tissues at constant ambient pressure; relevant to some technical profiles.
- In-Line Analyzer
- An oxygen analyzer installed in a gas-production or filling path.
- Inert-Gas Loading
- Absorption of nitrogen or helium into tissues during exposure to pressure.
- Injection Blending
- Adding oxygen at a controlled rate into compressor intake gas.
- Inspired PPO2
- The oxygen partial pressure in inhaled gas after accounting for pressure and physiology.
- Isobaric Gas Switch
- Changing inert-gas composition while remaining at essentially the same depth.
General Scuba Terms — I
- Inert Gas
- A gas not significantly metabolized by the body, such as nitrogen or helium in diving contexts.
- Inflator Hose
- A low-pressure hose supplying a BCD or drysuit inflator.
- Intermediate Pressure
- Regulator pressure between first and second stages.
- In-Water Recompression
- Recompression conducted underwater; it requires specialized protocols, equipment, and authorization and is not a recreational self-rescue technique.
- Inversion
- A diver orientation in which the feet are above the head, sometimes problematic in a drysuit.
- Immersion Diuresis
- Increased urine production associated with immersion and fluid redistribution.
- Incident Report
- A documented account of an accident, injury, near miss, or equipment failure.
- Inflator Button
- A control used to add or release gas from buoyancy equipment.
- Integrated Weight
- Ballast carried in releasable or fixed BCD pockets.
- Intertidal Zone
- The coastal area alternately exposed and submerged by tides.