Choice of Pony Bottle Size

Given that the individual action of the pony canteen is to accommodate a antecedent of breath gas for a controlled and advisable ascendance to the apparent in an emergency situation, it is a lot of important that the pony canteen admeasurement is called to be acceptable for that purpose. Even if accomplishing no decompression diving, the absolute affluence of breath gas have to still be acceptable to accumulation three phases of the ascent:

enough gas to acquiesce for a abbreviate aeon at abyss to bound array out any problems, if necessary, afore abiding to the surface

enough gas to accomplish a safe bit-by-bit ascendance to assurance stop abyss and

enough gas to do a complete assurance stop.

At the end of this time the pony canteen should still authority abundant gas to accommodate acceptable burden for bland breeze from the regulator aboriginal stage.

Pony canteen gas burning against assorted dive depths

Stage of ascent Max abyss 15 metres (49 ft) Max abyss 20 metres (66 ft) Max abyss 30 metres (98 ft) Max abyss 40 metres (130 ft)

Sort out problem: 2 account at max depth 150 litres (5.3 cu ft) 180 litres (6.4 cu ft) 240 litres (8.5 cu ft) 300 litres (11 cu ft)

Ascent from max abyss to 5 metres (16 ft): ascendance at 9 accent per minute (30 ft/min) 67 litres (2.4 cu ft) 113 litres (4.0 cu ft) 229 litres (8.1 cu ft) 379 litres (13.4 cu ft)

Safety stop: 3 account at 5 metres (16 ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft)

Total 352 litres (12.4 cu ft) 428 litres (15.1 cu ft) 604 litres (21.3 cu ft) 814 litres (28.7 cu ft)

Air accessible at 150 confined (2,200 psi)

Pony canteen 3 litre 450 litres (16 cu ft) 450 litres (16 cu ft) 450 litres (16 cu ft) 450 litres (16 cu ft)

Pony canteen 6 litre 900 litres (32 cu ft) 900 litres (32 cu ft) 900 litres (32 cu ft) 900 litres (32 cu ft)

The table aloft is complete to appearance gas captivated in just such a scenario: 2 account at abyss for "sort-out"; a safe amount of ascendance to 5 meters; followed by a 3 minute assurance stop. Calculations are based on a abundant breath amount of 30 L/min and an antecedent catchbasin burden of 150 bar (2,200 psi). In this accurate book the 3 litre pony is just acceptable for diving at 20 meters but not 30 meters. It is important that anyone selecting a pony canteen should do such an assay for his/her own breath rates, butt burden to be used, and appropriate ascendance profile, or yield admonition in the selection. Aswell it is important to agenda that back ecology of actual air is a key affair in ascentcitation needed, a submersible burden barometer clear at all times aswell needs to be absorbed to any pony canteen system.