Scuba & Nitrox Glossary: S
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 — S
- Sensor Cell
- An electrochemical or other sensing element used to measure oxygen.
- Set Point
- The target oxygen partial pressure maintained or selected in a closed-circuit rebreather.
- Standard Nitrox Mix
- A commonly stocked blend such as EAN32; actual composition must still be analyzed.
- Surface Equivalent Value (SEV)
- A way of expressing pulmonary oxygen exposure relative to breathing oxygen at the surface.
- SurMOD
- A planned maximum depth shallower than the calculated MOD, providing an additional operational buffer.
- Sensor Validation
- Checking an oxygen sensor against known gases and expected response.
- Solenoid Injection
- Automatic addition of oxygen to some rebreather loops through a solenoid valve.
- Stage Bottle MOD
- The maximum operating depth marked on a stage or decompression cylinder.
- Surface Equivalent Air Depth
- The air-depth comparison calculated for a Nitrox exposure.
- Sweet Mix
- Informal language for a blend selected to fit a specific planned depth.
General Scuba Terms — S
- Safety Stop
- A recommended pause during ascent on many no-decompression dives.
- SCR
- Semi-closed rebreather.
- Second Stage
- The regulator component that reduces intermediate-pressure gas to ambient pressure on demand.
- Silt-Out
- Severe visibility loss caused by disturbed sediment.
- SPG
- Submersible pressure gauge.
- Squeeze
- Pressure injury caused by unequal pressure between an air space and surrounding water.
- Stage Cylinder
- An additional cylinder carried for travel, decompression, or extended range.
- Surface Interval
- Time at the surface between dives.
- Surface Marker Buoy (SMB)
- A visible float or inflatable marker used to indicate diver position.
- S-Drill
- A team exercise rehearsing long-hose donation and hose deployment.
- Sea State
- A description of wave and surface conditions affecting dive operations.
- Shore Entry
- Entering the water from land using a site-appropriate route.
- Silt Out
- A severe loss of visibility caused by disturbed fine sediment.
- Surface Interval Credit
- The modeled reduction in residual inert gas during time at the surface.