36 to 42 Up to 3 hours - - 1 to 1-1/2
Over 3 hours - 5 6

42 to 48 Up to 1 hour - - 1-1/2
1 to 3 hours - 5 6-1/2
Over 3 hours - 10 11-1/2

48 to 54 Up to 1/2 hour - - 2
1/2 to 1-1/2 hour - 5 7
1-1/2 to 3 hours - 10 12
Over 3 hours - 20 22

54 to 60 Up to 20 minutes - - 2
20 to 45 minutes - 5 7
3/4 to 1-1/2 hour - 10 12
1-1/2 to 3 hours 5 15 22
Over 3 hours 10 20 32


When preparing to ascend the diver must tighten the air valve
in his helmet to increase his buoyancy; if the valve is closed
too much to allow the excess air to escape, his ascent will at
first be gradual, but the pressure of the water reduces, the
air in the dress expands, making it so stiff that he cannot
move his arms to reach the valve, and he is blown up, with
ever-increasing velocity, to the surface. While ascending he
should exercise his muscles freely during the period of waiting
at each stopping place, so as to increase the circulation, and
consequently the rate of deceleration.