Dive Terminology
- Air time remaining (ATR)
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The time you may remain at the current depth until an ascent at 9 m/min. (30 ft./min.) would result in surfacing with the reserve pressure.
- Central nervous system (CNS)
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A measure of central nervous system oxygen toxicity caused by exposure to increased partial pressure of oxygen (PO2) while diving.
- Closed-circuit rebreather (CCR)
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A diving mode used for dives performed with a rebreather that recirculates exhaled gas and removes carbon dioxide.
- Maximum operating depth (MOD)
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The greatest depth at which a breathing gas can be used before the partial pressure of oxygen (PO2) exceeds the safe limit.
- No decompression limit (NDL)
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A dive that does not require decompression time while ascending to the surface.
- Oxygen toxicity units (OTU)
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A measure of pulmonary oxygen toxicity caused by exposure to increased partial pressure of oxygen (PO2) while diving. One OTU is equivalent to breathing 100% oxygen at 1 ATM for 1 minute.
- Partial pressure of oxygen (PO2)
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The pressure of the oxygen in the breathing gas, based on depth and oxygen percentage.
- Pressure-based surface air consumption (PSAC)
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The change in pressure over time, normalized to 1 ATM.
- Respiratory minute volume (RMV)
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The change in gas volume at ambient pressure over time.
- Surface interval (SI)
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The amount of time that has elapsed since the completion of the last dive.
- Time to surface (TTS)
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The estimated amount of time it will take to ascend to the surface, including decompression stops.
- Volumetric surface air consumption (SAC)
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The change in gas volume over time, normalized to 1 ATM.