Air consumption. We plan to dive- always plan air consumption. Increases with pressure / depth. There is a growing exercise of effort and stress.

According to statistics of diving accidents from DAN and PADI, the most common cause is the lack of control the amount of air.

How to calculate the air consumption?

method 1

12 liter bottle, pressure 200 bar
200 x 12 = 2400 liters
The theoretical consumption of air at the surface is 20 liters per minute.
At a depth of 30 meters we have the pressure of 4 bar-20 x 4 = 80 liters
2400: 80 = 30 minutes

method 2

Breathe on the surface of the cylinder 12 liters / 200 bar and measure the time. Get real personal consumption at rest.
-For example, 120 minutes.
Depth of 30 meters, the pressure of 4 bar: 120: 4 = 30 minutes

For safety, you have to subtract 50 bar (reserve) and use the immersion and descent.