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 reserve pressure remaining.NOTE: If multiple tanks are included in gas consumption calculations, air time remaining is calculated using the combined pressure and reserve pressure of all tanks.
Decompression stops are included in the calculations, but safety stops are not.
- 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 required to safely ascend to the surface.
Decompression stops are included in the calculations, but safety stops are not.
- Volumetric surface air consumption (SAC)
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The change in gas volume over time, normalized to 1 ATM.