Bailout bottle
Encyclopedia
The term Bailout bottle or Bailout cylinder refers to a scuba cylinder carried by an underwater diver for use as an emergency supply of breathing gas in the event of a primary gas supply failure. A Bailout cylinder may be carried by a scuba diver in addition to the primary scuba set, or by a surface supplied diver using either free-flow or demand systems. The bailout gas is not intended for use during the dive except in an emergency.
meant to be used as an alternate air source
to allow a controlled ascent with any required decompression, in place of a controlled emergency swimming ascent
, which will not allow required decompression. A pony bottle
is an example of a bailout cylinder which has a standard diving regulator
with first and second stages. There are also significantly smaller cylinders which have the first stage — and in the smallest models also the second stage — integrated into the cylinder valve itself. A well known example of this class of bailout bottle is the Spare Air set, which can supply a few breaths to allow the diver to ascend at a safe rate, but not enough to do a decompression stop. This type of bailout bottle is typically placed in a holster that is attached to the diver.
Since their introduction in the 1980s, "Spare Air" bailout bottles have been the subject of debate within the diving community. The argument against them is that they do not have sufficient capacity to get a diver in many emergency situations back to the surface safely, and thus cause divers to feel a false sense of safety. The argument in favour is that "Spare Air" bottles are both less bulky and less complicated than pony bottles and that some air is better than none if a diver is in an emergency.
A review carried out by Scuba Diving magazine attempted to give a sense of from what depth bailout bottles of various capacities could get divers to the surface under maximum safe ascent rates, though the review cautioned that the reviewers were in controlled conditions and thus could not replicate the circumstances of an actual panicked diver. The review found that a 1.7-cubic-foot (0.24 L) bottle had sufficient air to get the reviewing diver from 45 feet (13.7 m) to the surface; a 3-cubic-foot (0.4 L) bottle from a depth of 70 feet (21.3 m); and a 6-cubic-foot (0.8 L) bottle from the maximum reviewed depth of 132 feet (40.2 m), which is the maximum depth recommended for recreational dives in some parts of the world.
In this application the intention is that the bailout cylinder should hold sufficient breathing gas for the diver to be able to reach a place of safety where more breathing gas is available, such as the surface or a diving bell. To achieve this the cylinder must contain enough gas to allow decompression if that is included in the planned dive profile. Cylinder volumes are generally at least 7 litres, and may in some cases be as much as twin 12 litre sets.
Bailout cylinders for use with scuba
For scuba, a "bailout bottle" or "self-contained ascent bottle" is a small diving cylinderDiving cylinder
A diving cylinder, scuba tank or diving tank is a gas cylinder used to store and transport high pressure breathing gas as a component of a scuba set. It provides gas to the scuba diver through the demand valve of a diving regulator....
meant to be used as an alternate air source
Alternate air source
In underwater diving, an alternative air source, or more generally alternative breathing gas source, is a secondary supply of air or other breathing gas used by the diver in an emergency...
to allow a controlled ascent with any required decompression, in place of a controlled emergency swimming ascent
Controlled Emergency Swimming Ascent
Controlled Emergency Swimming Ascent is a technique used by scuba divers as a safety measure when a diver has run out of breathing gas in shallow water and must return to the surface....
, which will not allow required decompression. A pony bottle
Pony bottle
A pony bottle is a small independently filled diving cylinder, often of only a few litres capacity, which forms an extended scuba set and which is fitted with its own independent regulator. In an emergency, such as exhaustion of the diver's main air supply, it can be used as an alternate air...
is an example of a bailout cylinder which has a standard diving regulator
Diving regulator
A diving regulator is a pressure regulator used in scuba or surface supplied diving equipment that reduces pressurized breathing gas to ambient pressure and delivers it to the diver. The gas may be air or one of a variety of specially blended breathing gases...
with first and second stages. There are also significantly smaller cylinders which have the first stage — and in the smallest models also the second stage — integrated into the cylinder valve itself. A well known example of this class of bailout bottle is the Spare Air set, which can supply a few breaths to allow the diver to ascend at a safe rate, but not enough to do a decompression stop. This type of bailout bottle is typically placed in a holster that is attached to the diver.
Since their introduction in the 1980s, "Spare Air" bailout bottles have been the subject of debate within the diving community. The argument against them is that they do not have sufficient capacity to get a diver in many emergency situations back to the surface safely, and thus cause divers to feel a false sense of safety. The argument in favour is that "Spare Air" bottles are both less bulky and less complicated than pony bottles and that some air is better than none if a diver is in an emergency.
A review carried out by Scuba Diving magazine attempted to give a sense of from what depth bailout bottles of various capacities could get divers to the surface under maximum safe ascent rates, though the review cautioned that the reviewers were in controlled conditions and thus could not replicate the circumstances of an actual panicked diver. The review found that a 1.7-cubic-foot (0.24 L) bottle had sufficient air to get the reviewing diver from 45 feet (13.7 m) to the surface; a 3-cubic-foot (0.4 L) bottle from a depth of 70 feet (21.3 m); and a 6-cubic-foot (0.8 L) bottle from the maximum reviewed depth of 132 feet (40.2 m), which is the maximum depth recommended for recreational dives in some parts of the world.
Bailout cylinders for use with surface supplied equipment
For commercial diving using surface supplied breathing gas, the bailout cylinder is in many cases required by health and safety legislation and approved codes of practice as an obligatory component of the diving system.In this application the intention is that the bailout cylinder should hold sufficient breathing gas for the diver to be able to reach a place of safety where more breathing gas is available, such as the surface or a diving bell. To achieve this the cylinder must contain enough gas to allow decompression if that is included in the planned dive profile. Cylinder volumes are generally at least 7 litres, and may in some cases be as much as twin 12 litre sets.