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Dive time Elapsed time between leaving the surface to descend, and returning to the surface at the end of a
dive.
Half-time After a change in ambient pressure, the amount of time required for the partial pressure of nitrogen
in a theoretical compartment to go half-way from its previous value to saturation at the new ambient
pressure.
Multi-level dive A single or repetitive dive that includes time spent at various depths and whose no-decompression
limits are not determined solely by the maximum depth attained.
No-decompression time The maximum amount of time a diver may remain at a particular depth without having to make
decompression stops or remain below a ceiling during the subsequent ascent.
No-decompression dive Any dive which permits a direct, uninterrupted ascent to the surface at any time.
NO DEC TIME Abbreviation for no-decompression time limit.
Repetitive dive Any dive whose no-decompression time limits are affected by residual nitrogen absorbed during
previous dives.
Residual nitrogen The amount of excess nitrogen remaining in a diver after one or more dives.
SURF TIME Abbreviation for surface interval time.
Surface interval time Elapsed time between surfacing from a dive and beginning a descent for the subsequent repetitive
dive.
Tissue group Theoretical concept used to model bodily tissues for the construction of decompression tables or
calculations.
