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79-441: The Core Facility of MSG occupies the upper half of the overall rack and includes the large work volume (WV), an airlock and electronics for control, housekeeping and investigation resources. The WV holds the experiment and related equipment. The work volume is approximately 3 feet (910 mm) wide, 2 feet (610 mm) high, and 1.5 feet (460 mm) deep with a usable volume of about 255 litres. This area can be sealed and held at

158-412: A caisson or sealed tunnel . The airlock may need to be large enough to accommodate a whole working shift at the same time. Locking in is usually a quick procedure, taking only a few minutes, while the decompression required for locking out may take hours. Underwater applications include: In saturation diving , airlocks are crucial safety elements; they serve as pressurized gateways to safely manage

237-508: A decontamination procedure and flushing are used instead of pressure change procedures. The first airlock patent was granted in 1830 to Thomas Cochrane , who came up with the idea to help facilitate underground tunnel construction. It was put into use in 1879 during an attempt to dig a tunnel under the Hudson river . The Apollo program involved developments in airlock technology, as airlocks are critical to allow humans to enter and exit

316-582: A pressure suit moves between environments of greatly different pressures, an airlock changes the pressure slowly to help with internal air cavity equalization and to prevent decompression sickness . This is critical in underwater diving , and a diver or compressed air worker may have to wait in an airlock for a number of hours in accordance with a decompression schedule . A similar arrangement may be used for access to airtight clean spaces, contaminated spaces, or unbreathable atmospheres, which may not necessarily involve any differences in pressure; in these cases,

395-414: A bailout block. If the main gas supply fails, the diver opens the bailout valve and emergency gas is supplied through the same final delivery system that provides breathing gas under normal circumstances. There is generally no requirement to change the helmet or mask, which reduces the complexity of the response and the number of possible complications or further failure modes. Bailout is reverted by closing

474-471: A dive to safely eliminate absorbed inert gases from the body tissues to avoid decompression sickness . The practice of making decompression stops is called staged decompression, as opposed to continuous decompression. The surface supplied diver is informed of the requirement for decompression stops, and if they are needed, the depths and durations of the stops, by the diving supervisor, who uses decompression tables , or software planning tools. The ascent

553-465: A dive, and the urgency of dealing with the problem is mainly due to the hypothermia or contamination hazard. A normal ascent should be possible, but exiting the water may be difficult due to the weight of water trapped in the suit. Damage to the upper part of the suit can cause a sudden venting of the air, resulting in a loss of buoyancy and possible uncontrolled descent, followed by flooding. The buoyancy loss may be so much that it cannot be supported by

632-428: A dive, only when doing surface support duty. Emergency procedures are the standardised and learned procedures for dealing with the reasonably foreseeable emergencies that may occur during a dive when equipment fails or environmental difficulties interrupt correct function. The diver is normally trained to manage these emergencies sufficiently to prevent injury and reduce them to an inconvenience which will usually require

711-413: A full-face mask which has both of these facilities. Some full-face masks do not have a free-flow option, and they are cleared by purging. Flooding of a free-flow helmet may be managed by increasing flow rate and either opening the neck seal with the fingers or tilting the head to allow the water to flow out through the exhaust port. The pressure of the breathing gas supply to a surface supplied diver

790-399: A hazardous environment. This is colloquially known as pneumo-breathing, and is a useful adjunct to the bailout set, as the gas supply is less limited. Pneumo-breathing may be used during the exit from a dive aborted after main gas hose failure as it allows the emergency gas supply to be conserved in case of a further failure. Pneumo gas can be supplied via the diver's own pneumo hose or that of

869-573: A hyperbaric escape chamber or lifeboat without significant pressure changes. In any hyperbaric treatment chamber capable of accommodating more than one person, and where it may be necessary to get a person or equipment into or out of the chamber while it is pressurized, an airlock is used. There will usually be a large airlock at the chamber entry capable of holding one or more persons, and a smaller medical lock for locking in medical supplies and food, and locking out waste. Airlocks are used in outer space, especially during human spaceflight , to maintain

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948-492: A medical lock for secure passage of medical necessities or emergency evacuations. Complex "split-level" systems, which house divers at different pressure levels for varied work depths, may necessitate additional airlocks. Decompression post-dive is a gradual process, often taking a full week. During this time, the airlocks allow divers to shift to a decompression chamber where pressure is progressively reduced back to surface levels. In emergencies, airlocks can facilitate transfer to

1027-513: A negative pressure, isolating the crew and the Station from possible hazards associated with the investigations that are taking place inside. An airlock under the WV can be accessed to bring objects in safely while other activities are going on inside MSG. The MSG has 40 cm diameter side ports (equipped with rugged gloves that are sealed to prevent leaks) for setting up and manipulating equipment in

1106-402: A self-standing subsystem of four colour cameras, two monitors, two analogue recorders and two digital recorders integrated into an International Sub-rack Interface Standard (ISIS) drawer. The command and monitoring panel monitors the facility status and performance and provides for manual operation of MSG by the crew. MSG was delivered to ISS during Expedition 5 , whereupon it was installed in

1185-407: A surface standby diver or the bellman. When two divers are working together each will be standby to the other, but there will generally be a surface standby diver and/or bellman as well for backup. It is usually possible for trapped diver to inform the surface of the problem, so the standby diver can tool up for the job. Unless the entrapment also cuts off the main breathing gas supply, entrapment

1264-458: A trickle of water through the cuff seal to a rapid escape of gas through a torn neck seal or damaged (or open) zipper followed by ingress of a large volume of water. There are two aspects to a catastrophic flood which put the diver at risk. Damage to the lower part of the suit can cause a sudden inrush of very cold water for winter users, or an inrush of contaminated water or chemicals for hazmat divers. This may not materially affect buoyancy during

1343-421: A valve to provide free-flow gas to the diver from a manually operated by-pass valve which usually directs the gas-flow over the interior surface of the faceplate/viewport. This flow of gas will blow off large water droplets and evaporate small droplets and light condensation, leaving the viewport clear. Though it tends to be noisy and wasteful of gas, it is trivially simple to do, does not require much practice, and

1422-419: A work site when the length of umbilical necessary to reach the work site is long enough to allow the diver to reach a hazard. It may alternatively be possible to use an unmanned tending point to restrict the ability of the diver to reach a hazard. The position of the in-water tender is chosen to restrict the distance between the tender and working diver so that last section of the umbilical between diver and tender

1501-430: Is a high risk contingency as the diver may be constrained from surfacing, and would be investigated immediately. If the diver cannot deal with the situation the standby diver would be sent in to assist. The possible consequences of a dry suit blowup are similar to a BCD blowup, and the method of management fairly similar. The instinctive reaction of trying to swim downwards is usually counterproductive, as it will prevent

1580-463: Is a room or compartment which permits passage between environments of differing atmospheric pressure or composition, while minimizing the changing of pressure or composition between the differing environments. An airlock consists of a chamber with two airtight doors or openings, usually arranged in series, which do not open simultaneously. Airlocks can be small-scale mechanisms, such as those used in fermenting , or larger mechanisms, which often take

1659-399: Is at a relatively high risk of drowning while in the water, and the priority is to prevent drowning while recovering the diver to a place where first aid can be given. In event of an irretrievably snagged or damaged umbilical and a need for in-water decompression, the original umbilical can be detached from helmet and harness and a replacement fitted in the water by a standby diver. The method

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1738-412: Is basically the same as radio voice protocol for other purposes, but the vocabulary may vary according to the operational circumstances. Loss of voice communications is not a directly life-threatening situation, but the risk of not being able to deal with an emergency is greatly increased as the surface team is unable to monitor the condition of the diver effectively and the diver is severely limited in

1817-499: Is high. If the water supply is too hot or too cold, the diver can adjust the flow rate which can help with small deficiencies, If the temperature is scalding the supply must be shut off at the suit immediately until corrected. Too cold can be tolerated without injury, but unless it can be corrected promptly the dive will be terminated. If a thin wet-suit is worn under the hot-water suit the diver can tolerate greater temperature variations with less chance of injury. A snagged umbilical

1896-474: Is less chance of aspiration, but vomit remains in the helmet or drains through into the diving suit, which is unpleasant, but not life-threatening. It may be possible to flush it out through the neck seal. The transparent faceplates of most helmets in current use are highly impact resistant and not easily damaged to the extent that they leak dangerously. If this does occur, the free-flow valve can be opened to increase internal pressure to reduce leak flow and purge

1975-441: Is made at the recommended rate until the diver reaches the depth of the first stop. The diver then maintains the specified stop depth for the specified period, before ascending to the next stop depth at the recommended rate, and follows the same procedure again. This is repeated until all required decompression has been completed and the diver reaches the surface. Once on the surface the diver will continue to eliminate inert gas until

2054-442: Is necessarily done by the divers who will be on that specific dive. The bellman is responsible for ensuring that the bell and its occupants are ready for descent or ascent, and associated for communications with the surface, though the diver can mention important things the bellman may have missed, and either diver can call a halt to lifting or lowering for reasons such as a difficulty in equalising. The bellman will normally stay in

2133-517: Is not generally immediately life-threatening. Assessing the problem is also facilitated if diver has hat video. An incapacitated diver is a diver who is unable, for some reason, to get themself to a place of safety, and for whom the intervention of a rescuer is necessary for survival. A variety of conditions may result in several forms of incapacitation. The most common form is a loss of consciousness or reduced level of consciousness, but severe injury and entrapment can also occur. An unconscious diver

2212-460: Is not safety critical. It is also done often in cold water. Some free-flow helmets and a few models of full-face mask pass the inlet air over the faceplate as default, and are thereby self-defogging. There are two ways to clear a demand helmet of water: The free-flow valve may be opened, or the purge button of the demand valve may be pressed, either of which will cause any water above the exhaust port to be driven out. The same procedures can be used on

2291-461: Is not usually an emergency in surface supplied diving as the lifeline or umbilical is always available as a route to the surface or the bell or stage, and can be used by the tender to assist the diver in most circumstances, but there may be occasions where the inability to establish neutral or positive buoyancy can make it difficult or dangerous to accomplish the dive task, in which case the dive should be ended. A leak dry suit leak can be anything from

2370-417: Is set at the gas panel, and does not automatically compensate for small depth changes the way most open circuit scuba first stages operate. To compensate for small variations due to moving around the workplace and variations in posture, the surface supplied demand helmet or full-face mask may be provided with a second stage valve spring tension adjuster screw, commonly referred to as "dial-a-breath", which allows

2449-412: Is short enough to prevent the diver from reaching the hazard. An in-water tender may also be used where the diver uses an extended umbilical or enters an enclosed space, to enhance safety or to facilitate handling of the umbilical. An unmanned tending point is an object provided between the bell and the work site through which the diver passes on the way to the work site, and which allows free movement of

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2528-479: Is simple – the new umbilical is secured to the diver's harness, the diver goes onto bailout, the gas supply on the original umbilical is shut down, and the umbilical connections are disconnected using the appropriate spanners (wrenches). The replacement gas supply hose is blown through to clear it of water, and fitted to the helmet. Communications cables are usually suitable for wet-connection, and this can be done if desired. The original umbilical may be disconnected from

2607-403: Is the responsibility of the diving supervisor, but any specific item may be delegated to the divers and attendants in the team. Checklists are commonly used to ensure that nothing is omitted and indicate completion. Most equipment is function tested as far as practicable during setup, and may be rechecked when dressing in the diver, and again on entering the water, as some checks can only be done in

2686-443: Is used as an analogy for locking out of a closed bell, but there is no pressure tight lock involved. The working diver will lock out of a wet bell on instruction from the supervisor, with a short length of umbilical, and make an integrity check of the bell. This will normally include a check that the main lifting cable is secure, the bell umbilical is clear and secure, the guide wires (clump weight lifting cable) are clear and secure, and

2765-675: The Nanoracks Bishop Airlock also allow payloads to be released into space with minimal air loss. Other examples of airlocks used in space include the Quest Joint Airlock and the airlock on Kibō (ISS module) . Transfer under pressure Surface supplied diving skills are the skills and procedures required for the safe operation and use of surface-supplied diving equipment . Besides these skills, which may be categorised as standard operating procedures, emergency procedures and rescue procedures, there are

2844-478: The 1980s, airlock technology has been used to explore newly detected chambers in the Egyptian pyramids , to prevent the contents from beginning to decompose due to air contamination. Civil engineering projects that use air pressure to keep water and mud out of the workplace use an airlock to transfer personnel, equipment, and materials between the external normabaric environment and the pressurized workplace in

2923-567: The BCD. After achieving neutral buoyancy, a normal ascent is usually possible, as it is seldom necessary to add air to the suit during ascent. The type of inflation hose connection can make a large difference to the urgency of the situation. The CEJN connector allows a much faster gas flow than the Seatec quick disconnect fitting, and the Seatec is considered safer by the DIR community for this reason. This

3002-634: The Destiny module. On March 21, 2008, during Expedition 16 , MSG was relocated to the Columbus module . On October 21, 2010, during Expedition 25 , MSG was transferred back to the Destiny module. The MSG accommodates small and medium-sized investigations from any disciplines including biotechnology, combustion science , life sciences, fluid physics, fundamental physics and materials science. Many of these experiments use chemicals, burning or molten materials or other hazards that must be contained. The MSG on

3081-554: The ISS in December 2020. It is "bell-shaped" and is designed to transfer payloads out from the ISS interior and into space. As of July 2023 it is the largest airlock of its kind on the station, capable of fitting "payloads as large as a refrigerator." Airlocks are used in air-to-air environments for a variety of reasons, most of which center around either preventing airborne contaminants from entering or exiting an area, or maintaining

3160-601: The ISS was utilized until 2010 for a large body of research. The MSG had operated on orbit for more than 3500 hours by 2010; used by various types of investigations, including material science, thermal management, protein crystal growth, life sciences, fire detection, combustion and technology demonstration. The versatility of the resources MSG provides makes it an ideal platform for microgravity research (Spivey 2006 - 2008). [REDACTED]  This article incorporates public domain material from Microgravity Science Glovebox (MSG) . NASA . Airlock An airlock

3239-496: The WV. A cold-plate provides cooling for experiment hardware and the air can be continuously circulated and filtered. Experiments are provided with 1 kW of power and cooling. Vacuum, venting, nitrogen gas dilution (that can keep the work volume oxygen volume fraction below the standard ISS atmosphere (nominally 21% by volume) down to 10 percent or less), power and data interfaces are also provided within MSG. A video system consists of

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3318-413: The ability to communicate a problem to the backup personnel, reducing the chances of prompt response in an emergency. The diver will generally communicate the problem to the surface by rope signals and abort the dive. The original method of communication between diver and surface was by pull signals on the lifeline, and these remain a useful emergency backup system. Divers are trained in rope signals, but

3397-544: The actual working skills required to do the job, and the procedures for safe operation of the work equipment other than diving equipment that may be needed. Some of the skills are common to all types of surface-supplied equipment and deployment modes, others are specific to the type of bell or stage, or to saturation diving . There are other skills required of divers which apply to the surface support function, and some of those are also mentioned here. The basic skills and procedures of surface supplied diving are those skills that

3476-487: The air pressure of the interior chamber. One common use of airlock technology can be found in some cleanrooms , where harmful or otherwise undesired particulates can be excluded by maintaining the room at a higher pressure than the surroundings, alongside other measures. Conversely, particulates are prevented from escaping hazardous environments, such as nuclear reactors , laboratories of biochemistry , and medical centers, by keeping negative room pressure - maintaining

3555-412: The appropriate class of diving, and are practiced during each dive with planned surface decompression. Depending on the employment of the diver and the contracts gained by the contractor, this may happen often, seldom or never, so the skill may or may not be kept well honed. The skills of operating a chamber for surface decompression may also be required of the diver, but will not be used by the diver during

3634-528: The automatic dump valve from releasing excess gas, while at the same time inflating the suit legs, making it difficult to fin, and if the boots slip off, impossible to fin. The diver must ensure that the dump valve is fully open, at the high point of the suit, and urgently disconnect the inflation hose. Many suits will release air at the neck or cuff seal if those are the highest point of the suit. It may be necessary to descend after this to compensate for rapid ascent, and to do this it may be necessary to dump gas from

3713-400: The bailout valve after another supply has been provided, either through the main supply of the umbilical, or from a pneumofathometer hose. The bailout cylinder is usually back-mounted and it is often not possible for the diver to reach the cylinder valve, so it is opened at the start of the dive, and checked regularly during the dive to ensure that the pressure does not drop. The bailout valve on

3792-419: The bell and tend the working diver's umbilical, as well as monitoring communications with the diver, main supply and on-board gas pressures at the bell panel, and emergency signals if the voice communications system fails. The bellman will also signal the diver to return to the bell if voice communications or main gas supply fails. Operation of the bell gas panel is the responsibility of the bellman . The term

3871-412: The bell does not appear to be at risk of fouling on any nearby structure or feature. The diver will report back that the bell integrity is OK and that they are leaving the bell to go to the work site. The procedures are very similar to surface umbilical management , but the bellman is the attendant. It may be necessary to use an in-water tender as well as the bellman to allow the working diver to access

3950-414: The buoyancy compensator. In this case alternative measures must be taken. The simplest case is to ditch sufficient ballast weight to allow the buoyancy compensator to regain neutral buoyancy, but this is not always possible, as there may not be sufficient ditchable weight to drop. The surface supplied diver can rely on the tender to compensate for loss of buoyancy by pulling up on the umbilical, or belaying

4029-662: The cabin without a space suit . When the International Space Station (ISS) first began to house humans in November 2000, it did not include an airlock, and all extravehicular activity had to be facilitated by the airlock on the Space Shuttle until the Quest Joint Airlock module was installed in July 2001. The first ever commercial space airlock was the Nanoracks Bishop Airlock , installed on

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4108-418: The concentrations have returned to normal surface saturation, which can take several hours, and is considered in some models to be effectively complete after 12 hours, and by others to take up to, or even more than 24 hours. Effective surface decompression requires the diver to get from the last in-water stop into the decompression chamber and be compressed to the correct pressure within 5 minutes, or increase

4187-410: The dive to be aborted, though temporary interruptions to main gas supply can sometimes be fully resolved at the surface. Loss of breathing gas is a safety-critical malfunction, and must be manageable by the diver without outside assistance over the short term. The diver generally carries an emergency scuba gas supply connected to the helmet or bandmask at the bailout valve, or to the full-face mask via

4266-439: The diver feels the need. Correct and effective voice communication is necessary for both safety and efficient underwater work. The skills are learned during training and exercised on almost every working dive. Voice communication protocols involve speaking clearly, providing the required information unambiguously and succinctly, checking that the information has been received and correctly understood, and taking turns to speak. This

4345-420: The diver may reasonably be expected to use during a dive when everything goes according to plan, and there are no emergencies. Many scuba skills are also common to surface supplied diving. The work of setting up the diving equipment on site is generally done by all members of the diving team, and they are usually all expected to be competent at all aspects of this work. The work is supervised and quality control

4424-410: The diver rises out of the water. This will take some time depending on the size of the holes, and agility will be seriously compromised while draining. If the exit is urgent or dangerous, larger drain holes will let the diver exit more quickly. The damage should not be difficult to repair if the slits are cut with reasonable care. Rescue procedures are the responsibility of the standby diver, who may be

4503-417: The diver to make adjustments to compensate for these variations. The knob can usually control cracking pressure from free-flow through to quite hard to breathe, and will usually compensate adequately for depth variations in the order of tens of metres. This skill is also well practiced by most divers, and is used on most dives. The knob is usually first adjusted during the pre-dive checks, and after that whenever

4582-433: The diver's ascent by hauling in the umbilical at the correct rate to facilitate decompression, and by locking off/belaying at the decompression stops. When diving from a bell, the bellman is the tender to the working diver. When there is a significant risk of the umbilical becoming snagged on underwater obstructions, it may be necessary to use an underwater tender at those areas, or to guide the umbilical past obstructions by

4661-433: The external or ambient pressure environment, sealing it, equalizing the pressure, and passing through the inner door is known as locking in . Conversely, locking out involves equalizing pressure, unsealing the outer door, then exiting the lock compartment to enter the ambient environment. Locking on and off refer to transfer under pressure where the two chambers are physically connected or disconnected prior to equalizing

4740-450: The form of an antechamber . An airlock may also be used underwater to allow passage between the air environment in a pressure vessel , such as a submarine , and the water environment outside. In such cases the airlock can contain air or water . This is called a floodable airlock or underwater airlock , and is used to prevent water from entering a submersible vessel or underwater habitat . The procedure of entering an airlock from

4819-459: The harness and cleared from the diver if this will help. A diving stage or basket is used to lower divers to the underwater work site and raise them back to the surface after the dive. This provides a relatively safe and easy way of entering the water and getting out again onto the deployment platform. In-water decompression is facilitated as the stage can be held at a reasonably constant depth. The divers' umbilicals are continuous and are tended from

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4898-400: The helmet is kept closed until it is needed to ensure that emergency gas is not used until it is needed. This is referred to by divers as "on at the back, off at the hat" and similar expressions. When bailing out on a free-flow helmet the flow rate must be reduced to a practicable minimum to conserve air, and the dive terminated immediately. The pneumofathometer hose has a smaller bore than

4977-407: The helmet of water. Tilting the helmet forward to lower the front will bring the faceplate down and may also reduce leakage and will help purge water from the helmet. In the event of a suit heating water supply failure that cannot be resolved promptly, the diver will abort the dive. This is a serious problem for divers using helium based breathing gas as heat loss is rapid and the risk of hypothermia

5056-560: The internal habitable environment on spacecraft and space stations when persons are exiting or entering the spacecraft. Without an airlock (or similar technology, such as a suitport ) the air inside would be rapidly lost upon opening the door due to the expansive properties of the gases that comprise breathable air , as described by Boyle's law . An airlock room is needed to decompress astronauts after they suit up in specialized space suits in preparation for extravehicular activity , and then to recompress them upon return. Airlocks such as

5135-411: The main breathing gas hose of the umbilical, but it is connected to the same gas supply at the gas panel, and can be used as a secondary route for surface supplied breathing gas for the diver if the main hose malfunctions. The open end of the pneumo hose can be inserted under the neck seal of the helmet or the face seal of a full-face mask, unless the helmet is sealed to the suit to prevent contamination by

5214-501: The most cost-efficient way to allow people to enter and exit these structures. Airlocks are utilized to maintain electron microscope interiors at near-vacuum so that air does not affect the electron path. Fermentation locks , such as those used in alcohol brewing, are a type of airlock which allow gases to escape the fermentation vessel while keeping air out. Parachute airlocks are necessary because airfoil collapse due to depressurization can result in dangerous loss of altitude. Since

5293-401: The pressure and locking in or out. Before opening either door, the air pressure of the airlock chamber is equalized with that of the environment beyond the next door. A gradual pressure transition minimizes air temperature fluctuations, which helps reduce fogging and condensation , decreases stresses on air seals, and allows safe verification of critical equipment. When a person who is not in

5372-446: The risk of decompression sickness sufficiently to incur a penalty of additional chamber decompression to compensate for the increased risk,. This requires the diver to get off the stage, and with the aid of the surface crew, strip off the dive gear and climb into the chamber entry lock, and for the surface crew to assist effectively and have the chamber main lock ready at the appropriate pressure. These skills are learned during training for

5451-405: The room at a lower pressure than the surroundings, so that air (and any particulates that it carries) cannot escape easily. A lesser-known application of an airlock is in architecture: inflatable buildings and air-supported structures such as pressurized domes require the internal air pressure to be maintained within a specific range so that the structure doesn't collapse. Airlocks are generally

5530-458: The set of signals may vary regionally. The US Navy and UK rope signals are different. There are two aspects of umbilical management: By the diver, and by the attendant. They work together to keep the umbilical from twisting, restraining the diver's movements, entanglement, and excess slack. The tender will control the amount of umbilical in the water, recover excess slack and coil it ready for further use. The tender may also be required to assist

5609-463: The spacecraft while on the Moon without losing too much air due to its scant atmosphere . During the 1969 Apollo 11 mission, there was no room that was primarily designed to be an airlock; instead, they used the cabin as an airlock. It had to be evacuated and depressurized before the door was opened, and then once the door was closed it had to be re-pressurized again before anyone could safely reenter

5688-448: The standby diver. There is a risk of aspiration of vomit trapped in the helmet air passages, with possibly fatal consequences. This problem is greatest in helmets and full-face masks with internal oro-nasal masks, where it will pass into the demand valve, and that which does not exit through the exhaust ports, will be an aspiration hazard unless flushed out before the next inhalation. A different problem occurs in free-flow helmets - there

5767-426: The surface. When divers leave the stage to work underwater under normal conditions they leave from the opposite side to that on which they entered, ensuring that their umbilicals pass through the framework of the stage, so they can be sure of finding their way back to the stage at the end of the dive. If it is necessary for any reason to abandon the stage, the divers leave it on the same side that they entered, so that

5846-498: The tender and diver working together and reporting results to the supervisor. Most checks are done before the diver is committed to the water, but some can only be done with the diver in the water. Before a dive the equipment must be thoroughly checked that it is suitable for the dive and in good working order, particularly those components which are part of the life-support system – the breathing apparatus, which includes: In-water checks include: Most demand helmets and bandmasks have

5925-417: The transfer of divers and support personnel between the saturation system (living quarters) and the diving bell , which shuttles divers to their underwater worksite. Airlocks in saturation diving are equipped with safety features such as pressure gauges , manual overrides , and interlocks . Saturation systems typically feature a variety of airlocks, including a stores lock for the transfer of supplies and

6004-441: The umbilical, allowing the diver to climb it, which may be safer if the umbilical passes over sharp edges or places where it may snag, making this a much lower risk problem than for a scuba diver. A badly flooded suit may contain so much water that the diver cannot climb out of the water because of the weight and inertia. In this case it may be necessary to cut a small slit in the lower part of each flooded leg to let water drain out as

6083-399: The umbilicals do not pass through the stage, and can be used to lift or lead the divers to the surface. Surface decompression is more common with stage and wet bell diving, which provide a better controlled ascent and exit from the water, but the procedures are much the same as described above The bell must be prepared for the dive, and this work is generally done by divers, though not all

6162-409: The use of some form of fairlead. A similar arrangement may be used to prevent the diver from approaching known hazards too closely. One way this can be done is to lower a large weighted hoop to a predetermined position, and for the diver to pass through this hoop on the way to the worksite. A decompression stop is a period a diver must spend at a relatively shallow constant depth during ascent after

6241-406: The water. The work may be described under the following headings: Some surface supplied diving equipment is heavy and cumbersome, and the diver is usually assisted with dressing in by a diver's attendant, who is often also a diver, so the skills of assisting a diver to dress in are necessary for the diver. The equipment involved includes: Pre-dive checks are done by the dive team as a group, with

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