Gas density tables are an important source of safety information for deeper diving (>40m).

The BSAC gas density tables show in tabular form:

  • Breathing gas densities for a variety of gas mixtures including air, nitrox, trimix and heliox at depths of 5m increments from 35 metres to 130 metres
  • Equivalent narcotic depths (END) for each gas mixture and depth increment


There are three tables in total. Two tables are for open circuit gas mixtures. One is based upon a partial pressure of oxygen (PO2) of 1.4 bar. This table is for use by open-circuit divers choosing safe dive gas. The other open-circuit table is based on a PO2 of 1.6 bar and is intended for use by open-circuit divers choosing accelerated decompression gases and rebreather divers choosing open-circuit bailout gases.

Each table shows a range of breathing gas mixtures for each depth increment that come within the safe gas density parameters for that depth. Each table also has a much smaller table of “ideal” gas mixtures for the depth increments.

BSAC releases gas density tables

BSAC has released three sets of gas density tables for members. Considered an important source of safety information based on empirical research, the tables are intended to inform planning for safer deeper diving (>40m).

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