■Check remaining cylinder pressure

Deep dives use gas quickly, so check your remaining cylinder pressure at each stage (a) through (e).
Do not use all the gas in your cylinder. Always surface with a reserve of at least 50 bar.

a) Before entry

Carefully check your assembled equipment for leaks.
Apply a mild soap solution (neutral detergent diluted with water) to the connection between the cylinder valve and the regulator first-stage/hose fittings, and look for bubbles.
Also check the primary and alternate second stages for leaks by listening for escaping gas and watching for bubbles in the water.

b) Immediately after descent

During the descent and once you reach depth, check both your equipment and your buddy's equipment for leaks or anything unusual.
If you notice a leak (for example, from a cylinder valve), notify your buddy and the dive leader and end the dive safely.

No leaks

c) During the dive

Monitor your pressure gauge frequently. Gas consumption is higher at depth than during shallow dives.

Pay close attention to remaining pressure

d) Before ascent

At an ascent rate of 10 m/min, it takes about 3 minutes to ascend from 30 m to the surface (not including a safety stop).
Begin your ascent with adequate remaining gas.

If you are using a 12-liter or 14-liter cylinder, a practical guideline is to start your ascent when your remaining pressure reaches about one-third of the starting pressure.

e) After exit

Confirm that your remaining pressure is at least 50 bar.
If you surfaced with less than 50 bar, plan the next dive more conservatively and begin your ascent earlier.

Leave at least 50 bar