the pressures in atmospheres yields a convenient formula (1 atm ≡ 101325 Pa): To simplify the algebra we will define . Combining the general formula and Pascal's law, we have: so that Since , the equivalent formula for the imperial system becomes Substituting R again, and noting that , we have the concrete formulas: Dive tables Although not all dive tables are recommended for use in this way, the Bühlmann tables are suitable for use with these kind of calculations. At 27 metres depth the Bühlmann 1986 table (for altitudes of 0–700 m) allows 20 minutes bottom time without requiring a decompression stop, while at 20 metres the no-stop time is 35 minutes. This shows that using EAN36 for a 27-metre dive can give a 75% increase in no-stop bottom time over using air at the same theoretical level of risk of developing symptoms of decompression sickness. US Navy tables have also been used with equivalent air depth, with similar effect. The calculations are theoretically valid for all Haldanean decompression models. References Underwater diving safety Dive planning