Spare Air Alternative air source

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charging spare air cylinder larger primary scuba cylinder


the smaller cylinders have combined first , second stage regulator directly mounted cylinder neck thread known spare air after commercially supplied unit of name. these can provide limited number of breaths out-of-air emergency , suitable relatively shallow dives without decompression. smaller 1.7 cu ft spare air provides approximately 30 breaths, , larger 3.0 cu ft approximately 60 breaths @ surface pressure. number of breaths provided in practice depend on diver s lung capacity, depth, exertion , state of mind. ascent 18 metres (60 ft) @ recommended rate of 9 metres per minute (30 ft/min) , typical residual minute volume of 15 litres per minute relaxed diver use approximately 60 litres of free air (volume @ surface pressure - approximately 2.1 cu ft.) dive profiles may adequate. manufacturers recommend these cylinders use within recreational diving limits , suggest little training required in use.


the small size , weight of these units makes them relatively convenient , easy carry, , more convenient travel larger cylinders. can handed off diver in need of air in emergency more conveniently larger cylinders. spare air unit commonly carried in small pouch can attached diver s harness or buoyancy compensator. unit may attached pouch safety leash if accidentally dropped underwater not lost.


recharging done through connector supplied unit purpose, , connects main cylinder valve decant air top-up. done diver before dive. button gauge provided allow diver check pressure.


since introduction in 1980s, spare air cylinders have been subject of debate within diving community. argument against them not have sufficient capacity diver in many emergency situations surface safely, , cause divers feel false sense of safety. arguments in favour spare air cylinders both less bulky , less complicated pony bottles, on , have no hoses or pressure gauges, , air better none in emergency.








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