The air consumption of each diver determines the possible diving time at the corresponding depth. An interesting value is the individual BreathMinuteVolume … here is the formula …
It’s nothing new: there are pressures in the scuba tank and at depth. At the surface we calculate with one bar of pressure, although the weathermen know that it can be more or less, per 10 meters then with one more bar each. So at 10 meters diving depth there are 2 bars of pressure.
Also in our diving equipment, the compressed air cylinder, the air is compressed. So more air just goes in there. Now in our calculation, it’s not important how much was in the scuba tank, but how much is missing.
If a 10-liter cylinder is missing 100 bars after the dive, that is 1000 liters of air.
When the diver is now at a depth of 10 meters, the partial pressure is twice that at the surface: 2 bars. This now means he can get by with the 1000 liters of air for only half as long.
Now to calculate how many liters of air the diver would have consumed per minute at the surface, we have to calculate the air consumed back to the surface level and divide it by the dive time.
So the formula for this is:
BreathMinutesVolume = (Air consumed in liters) divided by (Pressure at the bottom) divided by (Minutes of dive time)
an example:
Double 7 cylinder = 14 liters
Consumption = 110 bar
Bottom time = 61 minutes
Dive depth = 12.5 meters = 2.25 bar
AVM = (14 * 110)/ 2.25 / 61
In this case, the breathMinuteVolume = 11.22 liters per minute