Bailout bottle

Bailout bottle
	Filling a spare air bailout cylinder
Other names	Bailout cylinder, emergency gas supply
Uses	Emergency supply of breathing gas
Related items	Pony bottle

Last updated July 02, 2024

A bailout bottle (BoB) or, more formally, bailout cylinder is 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.^[1] The bailout gas is not intended for use during the dive except in an emergency, and would be considered a fully redundant breathing gas supply if used correctly. The term may refer to just the cylinder, or the bailout set or emergency gas supply (EGS), which is the cylinder with the gas delivery system attached. The bailout set or bailout system is the combination of the emergency gas cylinder with the gas delivery system to the diver, which includes a diving regulator with either a demand valve, a bailout block, or a bailout valve (BOV).

In solo diving, a buddy bottle is a bailout cylinder carried as a substitute for an emergency gas supply from a diving buddy. A bailout cylinder for recreational scuba diving is often a small cylinder, known as a pony bottle, with a normal scuba regulator set, or a smaller cylinder with a combined first and second stage integrated with the cylinder valve, known as "Soare air", after a well known example of the type.

Rebreathers also have bailout systems, often including an open-circuit bailout bottle.^[2]^[3]

Purpose

The purpose of the bailout cylinder is to provide a fully redundant breathing gas supply for use in emergencies where a single gas mixture is appropriate. If more than one mixture is necessary for the ascent, redundant breathing gas is typically split between two or more cylinders carried by the diver, and in penetration diving where the diver is constrained to use the same route for exit as for entry, cylinders may be staged, which is a term meaning stowed along the route of the guideline, to be retrieved on the return.

Bailout cylinders for use with scuba

For scuba, a "bailout bottle" or "self-contained ascent bottle" is a small diving cylinder 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 bailout cylinder is required equipment for a professional diver using scuba in some circumstances.^[4]

Types

A pony bottle is an example of a small 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.^[5] 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 carried in a holster that is attached to the diver's harness.^[6]

"Spare Air" bailout bottles, introduced in the 1980s, are very small cylinders with integral scuba regulators. Their disadvantage is that in many emergency situations they do not have sufficient capacity to get a diver back to the surface safely, and thus may cause divers carrying them to feel an unjustified sense of safety. Their advantage is that they are compact and easy to deploy, and that a small amount of air is better than none in an emergency.^[6]

Capacity

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 (14 m) to the surface; a 3-cubic-foot (0.4 L) bottle from a depth of 70 feet (21 m); and a 6-cubic-foot (0.8 L) bottle from the maximum reviewed depth of 132 feet (40 m), which is the maximum depth recommended for recreational dives by some training agencies.^[6] A bell diver must be able to return to the bell on the contents of the bailout cylinder, which will be influenced by the depth and umbilical length, and limited by the size of the bell entry lock manway.^[7]

Mounting arrangements

A pony bottle strapped to the back cylinder Pony bottle.jpg — A pony bottle strapped to the back cylinder

A bailout cylinder is defined by its function, and may be carried in any convenient way. The small "Spare Air" type is commonly carried in a pocket type holster which is strapped to the harness where it can easily be reached, usually somewhere on the front of a jacket style buoyancy compensator. Larger bailout cylinders may be strapped to the back cylinder, (see Pony bottle), or suspended from the harness D-rings along the side of the diver as a side-mount, or sling cylinder.^[2]^[8] Surface-supplied divers usually carry the bailout set on a back-mount harness, as this leaves the arms unencumbered for work.^[9]

Bailout systems used with rebreathers

In rebreather diving, bailout to open circuit is a procedure where the diver switches from breathing from the rebreather loop to open circuit. This is done when the loop is compromised for any reason, and is often done temporarily when there is some doubt that the gas in the loop is right for the depth. Bailout to open circuit may be a local switch-over at the bailout valve (BOV) to breathe gas directly from the diluent cylinder, or may be a switch to off-board gas, which is carried in an independent cylinder and is directly equivalent to open circuit bailout.^[2] This may be done through an off-board supply connected to the BOV or through a regular fully independent bailout set carried for the purpose. Both options may be available on deep dives with long decompression obligations.^[3] Occasionally rebreather divers will carry a bailout rebreather, when it is not practical to carry the required gas volume for open circuit bailout.

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^[10] and approved codes of practice^[11] 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 and there is no bell. Cylinder volumes are generally at least 7 litres, and may in some cases be as much as twin 12-litre sets.^{[ citation needed ]} Bailout sets used by closed bell divers must provide enough gas to return to the bell, and must fit through the bottom airlock door.^[7]

Bailout gas

The emergency gas supply must support life at any depth where it is likely to be used. It will almost always be used for ascent or return to the bell, so a relatively oxygen-rich mixture will usually be advantageous. In closed bell diving an unusually high oxygen partial pressure of 2.8 bar as used in therapeutic decompression was recommended by Association of Offshore Diving Contractors (AODC) and endorsed by the Diving Medical Advisory Council (DMAC) in 1981, on the assumption that if the diver does not make it back into the bell on the bailout gas, or loses consciousness to acute oxygen toxicity, the chances of successful resuscitation will be better than in the case of hypoxia.^[12] This strategy only holds when bailout is at constant pressure, the diver's airway is secured by a helmet, and there is a bellman to assist, as the risk of losing consciousness is relatively high.

Scuba divers cannot accept a high risk of oxygen toxicity convulsions and would usually consider an oxygen partial pressure of 1.6 bar to be the upper limit, though exposure at this pressure is likely to be of very short duration if an immediate ascent is started. It is common practice to use a non-optimised gas, as emergencies are not expected, and the same cylinder with the same gas may be carried on several dives, as long as the remaining quantity is sufficient.

The Diving Medical Advisory Council has more recently (2016) made a more conservative recommendation of an oxygen partial pressure for open circuit bailout for saturation divers of between 1.4 and 0.4 bar.^[13]

Alternatives

Alternatives to a bailout cylinder include:

A bailout rebreather, which must be ready for use at all times, and the diver must be competent to make the switch and secure the malfunctioning equipment to retain neutral buoyancy.
Team gas redundancy, as in buddy diving, where each diver in the team relies on the other divers to share gas in an emergency. This requires strict discipline and situational awareness from all members of the team to ensure that they are immediately available and competent to share gas if one of them has an out-of-gas emergency. In penetration diving using the rule of thirds and stage cylinders, team gas redundancy is applied.
Emergency ascent is practicable and may be acceptable as the planned contingency procedure when the total time to surface is short enough that the diver can do it on their last breath before the gas supply was cut off. This implies that no decompression stops are needed, and the distance to the free surface is short enough and clear of obstacles, and that the diver will not be required to exert themself much during the ascent to counteract negative buoyancy. For a fit and skilled diver this could be as deep as 30 m, but it is a decision a recreational diver must be competent to make for themself. A professional diver would not usually be allowed to dive to this depth without some form of emergency gas supply, as the risk is relatively high and there are reasonably practicable measures available to significantly reduce the risk.

Related Research Articles

A scuba set, originally just scuba, is any breathing apparatus that is entirely carried by an underwater diver and provides the diver with breathing gas at the ambient pressure. Scuba is an anacronym for self-contained underwater breathing apparatus. Although strictly speaking the scuba set is only the diving equipment that is required for providing breathing gas to the diver, general usage includes the harness or rigging by which it is carried and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.

Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.

A diving cylinder or diving gas cylinder is a gas cylinder used to store and transport high pressure gas used in diving operations. This may be breathing gas used with a scuba set, in which case the cylinder may also be referred to as a scuba cylinder, scuba tank or diving tank. When used for an emergency gas supply for surface supplied diving or scuba, it may be referred to as a bailout cylinder or bailout bottle. It may also be used for surface-supplied diving or as decompression gas. A diving cylinder may also be used to supply inflation gas for a dry suit or buoyancy compensator. Cylinders provide gas to the diver through the demand valve of a diving regulator or the breathing loop of a diving rebreather.

<span class="mw-page-title-main">Surface-supplied diving</span> Underwater diving breathing gas supplied from the surface

Surface-supplied diving is a mode of underwater diving using equipment supplied with breathing gas through a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no essential link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. Disadvantages are the absolute limitation on diver mobility imposed by the length of the umbilical, encumbrance by the umbilical, and high logistical and equipment costs compared with scuba. The disadvantages restrict use of this mode of diving to applications where the diver operates within a small area, which is common in commercial diving work.

<span class="mw-page-title-main">Scuba diving</span> Swimming underwater, breathing gas carried by the diver

Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.

Diver rescue, usually following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a diver to a place of safety. A safe place generally means a place where the diver cannot drown, such as a boat or dry land, where first aid can be administered and from which professional medical treatment can be sought. In the context of surface supplied diving, the place of safety for a diver with a decompression obligation is often the diving bell.

<span class="mw-page-title-main">Pony bottle</span> Small independent scuba cylinder usually carried for emergency gas supply

A pony bottle or pony cylinder is a small diving cylinder which is fitted with an independent regulator, and is usually carried by a scuba diver as an auxiliary scuba set. In an emergency, such as depletion of the diver's main air supply, it can be used as an alternative air source or bailout bottle to allow a normal ascent in place of a controlled emergency swimming ascent. The key attribute of a pony bottle is that it is a totally independent source of breathing gas for the diver.

In underwater diving, an alternative air source, or more generally alternative breathing gas source, is a secondary supply of air or other breathing gas for use by the diver in an emergency. Examples include an auxiliary demand valve, a pony bottle and bailout bottle.

Underwater breathing apparatus is equipment which allows the user to breathe underwater. The three major categories of ambient pressure underwater breathing apparatus are:

Scuba gas planning is the aspect of dive planning and of gas management which deals with the calculation or estimation of the amounts and mixtures of gases to be used for a planned dive. It may assume that the dive profile, including decompression, is known, but the process may be iterative, involving changes to the dive profile as a consequence of the gas requirement calculation, or changes to the gas mixtures chosen. Use of calculated reserves based on planned dive profile and estimated gas consumption rates rather than an arbitrary pressure is sometimes referred to as rock bottom gas management. The purpose of gas planning is to ensure that for all reasonably foreseeable contingencies, the divers of a team have sufficient breathing gas to safely return to a place where more breathing gas is available. In almost all cases this will be the surface.

An emergency ascent is an ascent to the surface by a diver in an emergency. More specifically, it refers to any of several procedures for reaching the surface in the event of an out-of-gas emergency, generally while scuba diving.

Scuba gas management is the aspect of scuba diving which includes the gas planning, blending, filling, analysing, marking, storage, and transportation of gas cylinders for a dive, the monitoring and switching of breathing gases during a dive, efficient and correct use of the gas, and the provision of emergency gas to another member of the dive team. The primary aim is to ensure that everyone has enough to breathe of a gas suitable for the current depth at all times, and is aware of the gas mixture in use and its effect on decompression obligations, nitrogen narcosis, and oxygen toxicity risk. Some of these functions may be delegated to others, such as the filling of cylinders, or transportation to the dive site, but others are the direct responsibility of the diver using the gas.

Rebreather diving is underwater diving using diving rebreathers, a class of underwater breathing apparatus which recirculate the breathing gas exhaled by the diver after replacing the oxygen used and removing the carbon dioxide metabolic product. Rebreather diving is practiced by recreational, military and scientific divers in applications where it has advantages over open circuit scuba, and surface supply of breathing gas is impracticable. The main advantages of rebreather diving are extended gas endurance, low noise levels, and lack of bubbles.

Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus, known as a scuba set. Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many also apply to surface-supplied diving. Some scuba skills, which are critical to divers' safety, may require more practice than standard recreational training provides to achieve reliable competence.

The following outline is provided as an overview of and topical guide to underwater diving:

The following index is provided as an overview of and topical guide to underwater diving: Links to articles and redirects to sections of articles which provide information on each topic are listed with a short description of the topic. When there is more than one article with information on a topic, the most relevant is usually listed, and it may be cross-linked to further information from the linked page or section.

Diving procedures are standardised methods of doing things that are commonly useful while diving that are known to work effectively and acceptably safely. Due to the inherent risks of the environment and the necessity to operate the equipment correctly, both under normal conditions and during incidents where failure to respond appropriately and quickly can have fatal consequences, a set of standard procedures are used in preparation of the equipment, preparation to dive, during the dive if all goes according to plan, after the dive, and in the event of a reasonably foreseeable contingency. Standard procedures are not necessarily the only courses of action that produce a satisfactory outcome, but they are generally those procedures that experiment and experience show to work well and reliably in response to given circumstances. All formal diver training is based on the learning of standard skills and procedures, and in many cases the over-learning of the skills until the procedures can be performed without hesitation even when distracting circumstances exist. Where reasonably practicable, checklists may be used to ensure that preparatory and maintenance procedures are carried out in the correct sequence and that no steps are inadvertently omitted.

The following index is provided as an overview of and topical guide to underwater diving:

References

↑ Larn, Richard; Whistler, Rex (1993). Commercial Diving Manual (3rd ed.). Newton Abbott, UK: David and Charles. ISBN 0-7153-0100-4.
1 2 3 Powell, Mark (8 April 2013). "What Bailout is Best for You? Rebreathers". TDI diver news. www.trisdi.com. Archived from the original on 9 April 2017. Retrieved 8 April 2017.
1 2 Staff. "Rebreather Safety & Bailout Procedures". www.apdiving.com. AP Diving. Archived from the original on 9 April 2017. Retrieved 8 April 2017.
↑ Sheldrake, S; Pedersen, R; Schulze, C; Donohue, S; Humphrey, A (2011). "Use of Tethered Scuba for Scientific Diving". In: Pollock NW, ed. Diving for Science 2011. Proceedings of the American Academy of Underwater Sciences 30th Symposium.
↑ "Bailout Bottle". scuba-info.com. Archived from the original on 15 July 2010. Retrieved 28 April 2010.
1 2 3 "Bailout Bottles". Scuba Diving. Bonnier Corporation. October 18, 2006. Archived from the original on 11 January 2010. Retrieved 28 April 2010. – Publishers of Scuba Diving magazine.
1 2 Staff (August 2016). "10 - General diving procedures". Guidance for diving supervisors IMCA D 022 (Revision 1 ed.). London, UK: International Marine Contractors Association. pp. 10–6.
↑ Heinerth, Jill (1 November 2023). "Air and a Spare". dan.org. Retrieved 24 April 2024.
↑ US Navy (1 December 2016). U.S. Navy Diving Manual Revision 7 SS521-AG-PRO-010 0910-LP-115-1921 (PDF). Washington, DC.: US Naval Sea Systems Command.
↑ "Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on 4 November 2016. Retrieved 3 November 2016– via Southern African Legal Information Institute.
↑ Staff (February 2014). IMCA D014 International Code of Practice for Offshore Diving (PDF) (Revision 2 ed.). London, UK: International Marine Contractors Association. Retrieved 30 January 2016.^{[ permanent dead link ]}
↑ Partial Pressure of O2 in Bail-Out Bottles. DMAC 04 (Report). Diving Medical Advisory Council. January 1981.
↑ Oxygen content in open circuit bailout bottles for heliox saturation diving. DMAC 04 revision 2 (Report). Diving Medical Advisory Council. May 2016.

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[Commercial_diving_manual-1] Larn, Richard; Whistler, Rex (1993). Commercial Diving Manual (3rd ed.). Newton Abbott, UK: David and Charles. ISBN 0-7153-0100-4.

[Powell_2013-2] 1 2 3 Powell, Mark (8 April 2013). "What Bailout is Best for You? Rebreathers". TDI diver news. www.trisdi.com. Archived from the original on 9 April 2017. Retrieved 8 April 2017.

[inspo_bailout-3] 1 2 Staff. "Rebreather Safety & Bailout Procedures". www.apdiving.com. AP Diving. Archived from the original on 9 April 2017. Retrieved 8 April 2017.

[RRR10115-4] Sheldrake, S; Pedersen, R; Schulze, C; Donohue, S; Humphrey, A (2011). "Use of Tethered Scuba for Scientific Diving". In: Pollock NW, ed. Diving for Science 2011. Proceedings of the American Academy of Underwater Sciences 30th Symposium.

[scuba-info-5] "Bailout Bottle". scuba-info.com. Archived from the original on 15 July 2010. Retrieved 28 April 2010.

[scubadiving.com-6] 1 2 3 "Bailout Bottles". Scuba Diving. Bonnier Corporation. October 18, 2006. Archived from the original on 11 January 2010. Retrieved 28 April 2010. – Publishers of Scuba Diving magazine.

[IMCA_D022_2016-7] 1 2 Staff (August 2016). "10 - General diving procedures". Guidance for diving supervisors IMCA D 022 (Revision 1 ed.). London, UK: International Marine Contractors Association. pp. 10–6.

[Heinerth_2021-8] Heinerth, Jill (1 November 2023). "Air and a Spare". dan.org. Retrieved 24 April 2024.

[USNDM_R7-9] US Navy (1 December 2016). U.S. Navy Diving Manual Revision 7 SS521-AG-PRO-010 0910-LP-115-1921 (PDF). Washington, DC.: US Naval Sea Systems Command.

[Diving_Regulations_2009-10] "Diving Regulations 2009". Occupational Health and Safety Act 85 of 1993 – Regulations and Notices – Government Notice R41. Pretoria: Government Printer. Archived from the original on 4 November 2016. Retrieved 3 November 2016– via Southern African Legal Information Institute.

[IMCA_D014-11] Staff (February 2014). IMCA D014 International Code of Practice for Offshore Diving (PDF) (Revision 2 ed.). London, UK: International Marine Contractors Association. Retrieved 30 January 2016.^{[ permanent dead link ]}

[DMAC_1981-12] Partial Pressure of O2 in Bail-Out Bottles. DMAC 04 (Report). Diving Medical Advisory Council. January 1981.

[DMAC_2016-13] Oxygen content in open circuit bailout bottles for heliox saturation diving. DMAC 04 revision 2 (Report). Diving Medical Advisory Council. May 2016.

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