The table above is constructed to show gas consumed in such a scenario: 2 minutes at depth for "sort-out"; a safe rate of ascent to 5 meters; followed by a 3 minute safety stop. Calculations are based on a heavy breathing rate of 30 L/min (1.06 cu ft/min) and an initial tank pressure of . In this particular scenario the 3 litre pony is just sufficient for diving at 20 meters but not 30 meters. A diver selecting a pony bottle would do a similar analysis for his/her own breathing rates, cylinder pressure to be used, and required ascent profile, or take advice in the selection. A submersible pressure gauge is required on the pony bottle regulator so that the pressure can be monitored during use to ensure that the diver surfaces before the gas runs out.