Check and assemble the gas cylinder

Choose a cylinder marked with the colour key that corresponds to the maximum depth planned for the dive:
1. 0-24m: RED marking, RED gas (60% O2) (NATO B-mixture)
2. 0-42 m: RED marking, RED gas (40% O2) (NATO C-Mixture)
3. 0-54 m: GREEN marking, GREEN gas (32.5% O2) (NATO D-mixture)
Check that the protective plug on the cylinder cannot be removed by hand. If it can, take another cylinder and return the other one for filling.
Make sure the gas cylinder is not damaged.
Remove any protective plugs from the cylinder valve with a 23 mm U-spanner.
Remove the protective plug on the hand wheel coupling for connecting the gas cylinder.
Check that the cylinder connection and hand wheel coupling are free from water, particles and other dirt. Make sure the O-rings on the hand wheel coupling are in position.
Blow the cylinder connection by quickly opening and re-closing the cylinder valves.
Place the cylinder in the cylinder cradle, rotate the cylinder to ensure that it is in the correct position and ensure that the cylinder valve connection is in the hole on the support arm. This must be checked, do not really know how it looks!
Screw the hand wheel coupling into the cylinder valve and tighten by hand only.
Check that the function of the by-pass arm is not obstructed.
Tension and attach the tension straps around the cylinder.