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Edwin Sandys (bishop)

Edwin Sandys (1519 – 10 July 1588) was an English prelate. He was Anglican Bishop of Worcester (1559–1570), London (1570–1576) and Archbishop of York (1576–1588) during the reign of Elizabeth I of England. He was one of the translators of the Bishops' Bible.

Early years and education
Edwin was born in 1519 at Esthwaite Hall, which is 1 mile south of Hawkshead, Cumbria, on the road to Newby Bridge. The Hall nestles in the valley and overlooks Esthwaite Water. Today it is still a family home, although the Sandys family now reside in the grander Graythwaite Hall, a few miles further south. He was the son of William Sandys and Margaret Dixon.

Whilst there is a theory that young Edwin received his early education at Furness Abbey, it is believed by Collinson that both Edmund Grindal and Edwin Sandys shared a childhood, quite probably in St Bees, and were educated together. A branch of the Sandys family lived at Rottington Hall near St Bees. The heralds in 1563 knew the family as"...of St Bees in the County of Cumberland", and Sandys himself recalled that he and Grindal had lived "familiarly" and "as brothers" and were only separated between Sandys's 13th and 18th Years. The St Bees registers are full of Sandys, and it thought likely that Sandys grew up at Rottington. However, his place of education is not recorded, though it is known that the Marian martyr John Bland was the schoolmaster of Sandys. Edwin Sandys kept one step behind Edmund Grindal in his subsequent career, succeeding him as bishop of London, and then archbishop of York.

He went up to St John's College, Cambridge, graduating BA in 1539 and then a Doctor of Divinity ten years later. In 1547 he was elected master of Catharine Hall and by the death of Edward VI in 1553 he was Vice Chancellor of the university.

Exile
On the death of King Edward, the Duke of Northumberland sought to avoid a Roman Catholic monarchy by placing Lady Jane Grey on the throne. He and his followers arrived in Cambridge to raise an army in East Anglia and demanded that Edwin Sandys preach a sermon. When the rebellion failed and Mary Tudor took the throne, Edwin was arrested and taken to the Tower of London. For this he is mentioned in Foxe's Book of Martyrs. Later he was moved to more comfortable conditions in Marshalsea prison where he made friends with the prison keeper who connived at his escape.

He went first to Antwerp and then Augsburg and Strasbourg where his wife joined him. His wife and infant son died there of a plague. He then lived in Zürich until the accession of Elizabeth I made it safe for him to return to England; on the day of Elizabeth's coronation. On 19 February 1559 he married Cicely Wilford, sister of James Wilford.

Archbishop of York
On his return he became successively Bishop of Worcester, Bishop of London and Archbishop of York. He helped in the translation of a new version of the Bishops' Bible. Sandys's own personal copy may be seen in the Hawkshead Grammar School Museum in Cumbria.

Along with other Marian exiles, who returned to positions of wealth and importance, Archbishop Sandys was concerned that true religion and sound learning would forever flourish in the land. They saw the necessity of education for religion's sake and the need for the Church of England to hold their own in discussion with Roman Catholics. To these ends Edwin Sandys founded Hawkshead Grammar School in 1585 and endowed it with sufficient land and property for it to offer a free education.

Sandys died on 10 July 1588, and was buried in Southwell Minster in Nottinghamshire.

Family
Sandys was twice married. His first wife, Mary Sandys, died in 1558 at Strasbourg. They had one son:
 * James Sandys (died 1557, Strasbourg)

On 19 February 1559, Sandys married Cicely Wilford, daughter of Thomas Wilford and sister of James Wilford. They had the following children:
 * Sir Samuel Sandys (1560–1623)
 * Sir Edwin Sandys (1561–1629), Treasurer of the Virginia Company of London
 * Sir Miles Sandys (1563–1645)
 * William Sandys (born 1565), died young
 * Margaret Sandys (1566–1611), married Anthony Aucher
 * Thomas Sandys (1568–c. 1634), colonist, a first settler of Jamestown, Virginia
 * Anne Sandys (1570–c. 1629), married Sir William Barne
 * Henry Sandys (1572–1626)
 * George Sandys (1578–1644), traveller and poet, colonist in Virginia

In 1604 Cicely Sandys enlisted the support of Anne of Denmark in an unsuccessful attempt to found a university at Ripon in Yorkshire.

title: Edwin Sandys (bishop)


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Diver communications

Diver communications are the methods used by divers to communicate with each other or with surface members of the dive team. In professional diving, diver communication is usually between a single working diver and the diving supervisor at the surface control point. This is considered important both for managing the diving work, and as a safety measure for monitoring the condition of the diver. The traditional method of communication was by line signals, but this has been superseded by voice communication, and line signals are now used in emergencies when voice communications have failed. Surface supplied divers often carry a closed circuit video camera on the helmet which allows the surface team to see what the diver is doing and to be involved in inspection tasks. This can also be used to transmit hand signals to the surface if voice communications fails. Underwater slates may be used to write text messages which can be shown to other divers, and there are some dive computers which allow a limited number of pre-programmed text messages to be sent through-water to other divers or surface personnel with compatible equipment.

Communication between divers and between surface personnel and divers is imperfect at best, and non-existent at worst, as a consequence of the physical characteristics of water. This prevents divers from performing at their full potential. Voice communication is the most generally useful format underwater, as visual forms are more affected by visibility, and written communication and signing are relatively slow and restricted by diving equipment.

Recreational divers do not usually have access to voice communication equipment, and it does not generally work with a standard scuba demand valve mouthpiece, so they use other signals. Hand signals are generally used when visibility allows, and there are a range of commonly used signals, with some variations. These signals are often also used by professional divers to communicate with other divers. There is also a range of other special purpose non-verbal signals, mostly used for safety and emergency communications.

Function
For safety and efficiency, divers may need to communicate with others diving with them, or with their surface support team. The interface between air and water is an effective barrier to direct sound transmission, and the natural water surface is also a barrier to visual communication across the interface due to internal reflection, particularly when not perfectly smooth. The equipment used by divers and the pressurised environment are also hindrances to sound-based communication, and the encumbrance of diving equipment, relatively low light levels, and low visibility of many diving environments also hinders visual communication.

Communication is most critical in an emergency, where high stress levels make effective communication more difficult, and the circumstances of the emergency may make the communication physically more difficult. Voice communication is natural and effective where it is practicable, and most people rely on it for fast and accurate communication in most circumstances.

The general requirements for an effective system for diver communication are that all the people who will use it have access to the system, that it functions effectively in the specific environment, that the people who wish to use it are familiar enough with it to communicate quickly, accurately and unambiguously with each other, and that the system has sufficient range to work when needed. A simple, logical and widely standardised system of signals is more effective at meeting these requirements. Several such systems have been developed using different equipment and suited for different circumstances. These include sound-based systems, visual systems and tactile systems.

History
The original communication between diver and surface attendant was by pulls on the diver's lifeline. Later, a speaking tube system, patented by Louis Denayrouze in 1874, was tried; this used a second hose with a diaphragm sealing each end to transmit sound, but it was not very successful. A small number were made by Siebe-Gorman, but the telephone system was introduced soon after this and since it worked better and was safer, the speaking tube was soon obsolete, and most helmets which had them were returned to the factory and converted. In the early 20th century electrical telephone systems were developed which improved the quality of voice communication. These used wires incorporated into the lifeline or air line, and used either headsets worn inside the helmet or speakers mounted inside the helmet. The microphone could be mounted in the front of the helmet or a contact throat-microphone could be used. At first it was only possible for the diver to talk to the surface telephonist, but later double telephone systems were introduced which allowed two-divers to speak directly to each other, while being monitored by the attendant. Diver telephones were manufactured by Siebe-Gorman, Heinke, Rene Piel, Morse, Eriksson, and Draeger among others. This system was well-established by the mid-20th century, has been improved several times as new technology became available, and is still in common use for surface-supplied divers using lightweight demand helmets and full-face masks. The introduction of closed circuit video to monitor the interior of diving bells, and to provide the supervisory team with direct feedback on the diver's work activities has expanded the capacity to provide useful advice to the working diver, and to keep track of the stand-by diver or 's activity in an emergency, making coordinated activity easier and more effective.

More recently, through-water systems have been developed which do not use wires to transmit the signal. They were first developed for the U.S. Navy in the late 1960s. An early system for recreational scuba, the Wet Phone, was launched by Sound Wave Systems in 1977, but failed. By the mid-1980s miniaturized electronics made it possible to use single-sideband modulation, which greatly improved intelligibility in good conditions. By 1988 several systems using single side-band were found satisfactory by the US Navy for intelligibility and range, and mostly satisfactory for ergonomics, reliability and maintainability. Through-water systems allow communications over limited distances between divers and with the surface, usually using a push to talk system, which minimises power consumption by transmitting only on demand. They are not yet in general use by recreational divers due to cost and the need for a full-face mask.

Scope
Surface supplied diving uses the widest range of equipment and methods. As of 2021, hard wired (cable) voice communications are still the primary method, supported in major commercial applications by one-way closed circuit video but line pull signals are also used as an emergency backup, and through-water voice systems may be used as emergency backup for closed diving bells. Local communication between divers includes hand signals and text written on slates.

Scuba diving can be done with cable voice communications, but the restriction on mobility makes this an unusual choice as it negates the primary reason for using scuba. Through-water voice communications do not have the same restriction on diver mobility, which is often the reason for choosing scuba for professional diving, but are more complex, more expensive, and less reliable than the hard-wired systems. There are some recreational applications for through-water voice communications for scuba, but this method is usually used for professional applications such as military and scientific diving, and almost all recreational diving relies on hand signals, light signals and writing slates for diver-to-diver communications, with the very few communications between diver and surface restricted to pre-arranged emergency signals. Breath-hold divers use a subset of the recreational diving hand signals where applicable, and have some additional hand-signals specific to freediving.

The presence of divers in the water during a diving operation exposes the divers to risks from passing waterborne traffic, and there are internationally standardised shape, light and flag signals to indicate that the diving support vessel is restricted in its ability to maneuver and that there are divers in the water.

Equipment
Both hard-wired (cable) and through-water electronic voice communications systems may be used with surface supplied diving. Wired systems are more popular as there is a physical connection to the diver for gas supply in any case, and adding a cable does not make the system any different to handle. Wired communications systems are still more reliable and simpler to maintain than through-water systems, and do not require the diver to carry a power source. The communications equipment is relatively straightforward and may be of the two-wire or four-wire type. Two wire systems use the same wires for surface to diver and diver to surface messages, whereas four wire systems allow the diver's messages and the surface operator's messages to use separate wire pairs, allowing simultaneous speech in both directions. A standard arrangement with wired diver communications is to have the diver's side normally on, so that the surface team can hear anything from the diver at all times except when the surface is sending a message on a two-wire system. This is considered an important safety feature, as the surface team can monitor the diver's breathing sounds, which can give early warning of problems developing, and confirms that the diver is alive.

Through-water communications systems are more suitable for scuba as the diver is not encumbered by a communications cable, but they can be fitted to surface supplied equipment if desired. Most through-water systems have a push to talk system, so that high power is only used to transmit the signal when the diver has something to say. For commercial diving applications this is a disadvantage, in that the supervisor cannot monitor the condition of the divers by hearing them breathe.

Through-water communication systems are of two basic types. Acoustic systems provide one-way communications from the surface to divers. An audio signal emitted by a submerged transducer travels through the water to the divers, who can hear the sound directly, without signal receiving equipment. Amplitude modulated (AM) and single sideband (SSB) systems provide two-way communications between divers and between the surface and divers. Both the AM and SSB systems require electronic transmitting and receiving equipment worn by the divers, and an immersed transducer connected to the surface unit. SSB systems perform better around obstacles, and AM systems give a stronger and often clearer signal for the same power, but are restricted to line-of-sight use.

The diver's speech is picked up by the microphone and converted into a high frequency sound signal transmitted to the water by the omnidirectional transducer. The signal can bounce off the bottom and surface and other obstructions, which can extend the range around obstructions, but will also degrade the signal due to interference effects caused by varying path lengths of different routes. When a receiving transducer picks up the signal, the ultrasonic signal is converted to an amplitude modulated electrical signal, amplified and converted to sound by the earphone. The through-water communications sets carried by the divers are battery powered.

The push-to-talk (PTT) method is the most widely available system for through-water communications, but some equipment allows continuous transmission, or voice activated mode (VOX).

Push to talk is simple, efficient, and the preferred mode of many divers. It transmits only when the button is pressed, and saves power by not transmitting when the diver has nothing to say, but requires the diver to use a hand to transmit. Users take turns to speak and listen. This is normal communications protocol, and encourages clear communication, but does not allow audio monitoring of the diver between communications.

Voice activated means that the unit is intended to transmit when the diver's voice activates the microphone. If there is sufficient sound level generated at the microphone, the unit will transmit. This would run the battery down more rapidly when the background noise level is sufficient to activate transmission, but it allows hands-free communications.

Continuous transmission is a mode where one diver transmits continuously. This is hands free, but all audible noise will be heard by others on the same channel and within range. Open circuit breathing apparatus generally produces considerable exhalation bubble noise.

Through-water systems are also used for back-up to the wired communications via the umbilical generally used in closed diving bells. These systems are used in case of failure of the wired system, and do not rely on the integrity of the bell umbilical, so will work if the umbilical is severed and the bell lost. They operate between a battery powered transducer on the bell and a surface unit using a similar acoustic signal to those used for wireless diver communications. Single side-band suppressed carrier systems may be used, and a 27 kHz frequency with 4.2 kHz bandwidth is typical. Divers breathing helium may need a decoder system (also called unscrambling), which reduces the frequency of the sound to make it more intelligible.

Voice communication protocol
Underwater voice communication protocol is like radio communication protocol. The parties take turns to speak, use clear, short sentences, and indicate when they have finished, and whether a response is expected. Like radio, this is done to ensure that the message has a fair chance of being understood, and the speaker is not interrupted. When more than one recipient is possible, the caller will also identify the desired recipient by a call up message, and will also usually identify themselves. The surface caller should also give the diver a chance to temporarily suspend or slow down breathing, or stop using noisy equipment, as breathing noise generated by gas flow through the inlet and bubble noise from the exhaust is often so loud that the message can not be heard over it.

Hyperbaric speech distortion
The process of talking underwater is influenced by the internal geometry of the life support equipment and constraints on the communications systems as well as the physical and physiological influences of the environment on the processes of speaking and vocal sound production. The use of breathing gases under pressure or containing helium causes problems in intelligibility of diver speech due to distortion caused by the different speed of sound in the gas and the different density of the gas compared to air at surface pressure. These parameters induce changes in the vocal tract formants, which affect the timbre, and a slight change of pitch. Several studies indicate that the loss in intelligibility is mainly due to the change in the formants.

The difference in density of the breathing gas causes a non-linear shift of low-pitch vocal resonance, due to resonance shifts in the vocal cavities, giving a nasal effect, and a linear shift of vocal resonances which is a function of the velocity of sound in the gas, known as the. Another effect of higher density is the relative increase in intensity of voiced sounds relative to unvoiced sounds. The contrast between closed and open voiced sounds and the contrast between voiced consonants and adjacent vowels decrease with increased pressure. Change of the speed of sound is relatively large in relation to depth increase at shallower depths, but this effect reduces as the pressure increases, and at greater depths a change in depth makes a smaller difference.

Helium speech unscramblers are a partial technical solution. They improve intelligibility of transmitted speech to surface personnel.

Video communications
Closed circuit video is often fitted to the helmets of surface supplied commercial divers to provide information to the surface team of the progress of work done by the diver. This may allow the surface personnel to direct the diver more effectively to facilitate the completion of the task. Voice communication is always provided when diver video is used. The communications cables for these systems are part of the diver's umbilical. Video may also be used to monitor the occupants of a closed diving bell.

Hand signals
Hand signals are a form of sign system used by divers to communicate when underwater. Hand signals are useful whenever divers can see each other, and some can also be used in poor visibility if in close proximity, when the recipient can feel the shape of the signaller's hand and thereby identify the signal being given. At night the signal can be illuminated by the diver's light. Hand signals are the primary method of underwater communication for recreational scuba divers, and are also in general use by professional divers, usually as a secondary method.

Divers who are familiar with a sign language such as American sign language and equivalents may find it useful underwater, but there are limitations due to the difficulty of performing some of the gestures intelligibly underwater with gloved hands and often while trying to hold something.

RSTC hand signals
Member agencies of the Recreational Scuba Training Council (RSTC) in the United States have recognised a standardised set of hand signals intended for universal use, which are taught to diving students early in their entry-level diving courses.

These hand signals provide the following information:

 * I am out of breath! Hands indicate rising and falling chest.
 * Go that way: Fist with one hand, thumb extended and pointing in the direction indicated.
 * Go under, over or around: With palm down, hand motion used to indicate intended route to go under, over or around an obstacle.

Other commonly used hand signals and variations
Diving signals sometimes differ between groups of divers. There are regional variations and variations that relate to the type of diving. One of the items with the largest range of variations is how divers indicate the remaining gas pressure in their cylinders. Some variations include:
 * The throat cut signal: "general danger" or "emergency".
 * Tapping the mouthpiece: "share air".
 * Pointing at the ear: "listen!"
 * Hand cupped behind ear: "listen!"
 * Pointing at someone changes the reference of the next signal from "I" to the diver pointed at.
 * Flat hand swept over top of head, palm down: "I have a ceiling". This can indicate the diver has gone into or that there is a solid obstruction overhead. When ascending it means "stop here". (this is my decompression ceiling, or we are ascending too fast, or just generally stop ascending at this depth).
 * Moving hand across torso in wave motion: "Current"

Divers sometimes invent local signals for local situations, often to point out local wildlife. For example:
 * I see a hammerhead shark: Both fists against sides of head
 * I see a lobster: Fist with index and middle finger pointed out horizontally and alternately waggling up and down
 * I see an octopus: Back of hand or wrist covering mouth, all fingers pointing outward from mouth and wiggling
 * I see a shark: Hand flat, fingers vertical, thumb against forehead or chest
 * I see a turtle: Hands flat one on top of each other, palms down, waving thumbs up and down together

Instructor signals:
 * You (all) watch me. (usually before demonstrating a skill): Point at diver(s) with forefinger, point at own eyes with forefinger and middle finger, point at own chest with forefinger.
 * You try that now, or do it again: Gesture with open hand palm up towards student after a demonstration of a skill.

Dive light signals
The focused beam of a dive light can be used for basic signalling as well. Normally a diver does not shine a torch / flashlight in another diver's eyes but directs the beam to his or her own hand signal.
 * OK signal: Drawing a circle on the ground in front of buddy.
 * Attention please! Waving the torch up/down.
 * emergency! Rapid, repeated, back and forth horizontal motion

Touch signals
There are a few tactile signals in use by penetration divers for controlling a blind passage through an area of extremely low visibility, or where the restrictions do not allow the divers to see each other well enough to use hand signals. The Rimbach system of touch contact signalling:
 * Push forward = go,
 * Pull back = back up,
 * Squeeze = stop.

Line signals
Also known as rope signals, these are generally used in conditions of low visibility where a diver is connected to another person, either another diver or a line tender on the surface, by a rope, airline hose or diver's umbilical. These date back to the time of the use of standard diving dress. Some of these signals, or pre-arranged variants, can be used with a surface marker buoy. The diver pulls down on the buoy line to make the buoy bob in an equivalent pattern to the rope signal. Effective line signals need a free line without much slack – before attempting a line signal, the slack must be taken up, and the line pulled firmly. Most signals are acknowledged by returning the same signal, which shows that it was received accurately. Persistent failure to acknowledge may indicate a serious problem and should be resolved as a matter of urgency. There are several systems in use, and it is necessary to have agreement between diver and tender before the dive.

British Sub-Aqua Club
BS-AC have a very small set of rope signals. Most of them have the same meaning as the equivalent commercial or Royal Navy signal.

Tender to diver
 * One pull – Are you OK?
 * Two pulls – Stay put.
 * Three pulls – Go down.
 * Four pulls – Come up at normal rate.
 * Five or more pulls – Emergency, come up to the surface!

Diver to tender
 * One pull – I am OK.
 * Two pulls – I am stationary.
 * Three pulls – I am going down.
 * Four pulls – I am coming up.
 * Five or more pulls – Emergency, bring me to the surface! (no reply required)

Public Safety Divers
Public safety divers and some recreational divers use the following line signals while conducting circular and arc searches underwater.

Tender to diver
 * One pull – Are you OK?
 * Two pulls – Stop, take out slack, reverse direction.
 * Three pulls – Come to the surface.
 * Four pulls – Stop, stand by, don't move. (there could be danger ahead or a boat entering the search area)

Diver to tender
 * One pull on the line – OK.
 * Two pulls – Pay out more line.
 * Three pulls – Object found.
 * Four or more pulls – Assistance needed.

Commercial diving
Rope signals used in the UK and South Africa include the following:

Signals are combinations of pulls and bells, A pull is a relatively long steady tension on the line. Bells are always given in pairs, or pairs followed by the remaining odd bell. They are short tugs, and a pair is separated by a short interval, with a longer interval to the next pair or the single bell. The technique and nomenclature derive from the customary sounding of the ships bell every half-hour during the watches, which is also performed in pairs, with the odd bell last. One bell is not used as a diving signal as it is difficult to distinguish it from a jerk caused by temporarily snagging the line.

Attendant to diver:

General signals:
 * 1 pull – Calling for attention, are you OK?
 * 2 pulls – I am sending down a rope's end. (or other pre-arranged item)
 * 3 pulls – You have come up too far, go back down until we stop you.
 * 4 pulls – Come up.
 * 4 pulls and 2 bells – Come to the surface immediately. (often for surface decompression)
 * 4 pulls and 5 bells – Come up your safety float line.

Direction signals:
 * 1 pull – Search where you are.
 * 2 bells – Go out along the or distance line, or straight out away from tender.
 * 3 bells – Facing shot or tender, go right.
 * 4 bells – Facing shot or tender, go left.
 * 5 bells – Come back towards shot or, or back along the jackstay.

Diver to attendant:

General signals:
 * 1 pull – To call attention, or have completed the last instruction.
 * 2 pulls – Send down a rope's end. (or other pre-arranged item)
 * 3 pulls – I am going down.
 * 4 pulls – I wish to come up.
 * 4 pulls and 2 bells – Help me up.
 * 5 or more pulls – Emergency, pull me up immediately!
 * succession of 2 bells – I am fouled and need standby diver to assist.
 * succession of 3 bells – I am fouled but can get clear without assistance.
 * 4 pulls and 4 bells – I am trying to communicate on voice comms.

Working signals:
 * 1 pull – Hold on or stop.
 * 2 bells – Pull up.
 * 3 bells – Lower.
 * 4 bells – Take up slack on the lifeline or lifeline is too tight.
 * 5 bells – I have found, started or completed the work.

Royal Navy
All signals start with a pull to attract attention, and this must be acknowledged before the actual signal is made. Royal Navy (RN) signals include short, paired "bells" and longer "pulls". The RN signals are almost identical to the rope signals used by commercial divers in the UK and South Africa.

US Navy
The US Navy also has a standard set of line signals. These include general signals from diver to tender, search signals, and emergency signals. The signal to change from general to search signals or vice versa is seven pulls, and the meaning of the signals may vary depending on whether it is given by the diver or the tender. Most signals are acknowledged by returning the same signal, confirming that the signal was received correctly.

Slates
Written messages on plastic slates can be used to convey complex messages with a low risk of misunderstanding. Slates are available in various sizes and are usually hard white plastic with a matte finish, suitable for writing on with a pencil. They can be stored in various ways, but in a pocket or bungeed to the wrist are popular methods. Clipped to the diver by a lanyard is another method, but there is a greater risk of entanglement. Slates may be used to record information to be used on the dive, such as decompression schedules, to discuss matters of importance for which hand signals are not sufficient, and to record data collected during the dive. Waterproof paper wet-notes are a compact equivalent, and pre-printed waterproof data-sheets and clip-board are routinely used by scientific divers for recording observations.

Cave line markers
Cave arrows, Line arrows or Dorff markers (after Lewis Holtzendorff) are plastic arrowhead markers which are hooked onto a cave line by wrapping the line around the arrow through the slots. They are used to indicate the direction to the exit, and can be identified by feel. The message is simple, but of critical importance, as if a diver does not know which way to go at a line junction there is a risk of serious trouble. Line arrows are also used at a junction on the permanent line, and at a tie-off, so when the diver gets back to the tie-off, he or she can identify which way to turn.

Non-directional and hybrid personal line markers are used to indicate the identity of a diver who has passed along the line and has not yet returned to that point. They are attached to the line in the same way as cave arrows, and are deployed on the way into the cave, usually at critical points such as forks or jumps, and are used to indicate to other divers that someone is further in along the line. They are marked to identify the diver, and are recovered by the diver on the way out. Cookies (round markers), rectangular referencing exit markers and clothes pegs are used for this purpose. The round and rectangular markers are attached to the line in the same way as arrows, and may be personalised in any way that the owners can easily recognise. Colour is often used, but as there are a limited number of standard colours available, and they are often poorly distinguishable in the dark, modifications to shape may be used which can be recognised by touch.

Arrows should always be placed on the outbound side of an intersection as this is unambiguous. Sometimes there is more than one exit from an intersection. Both should be marked with arrows, but the preferred exit can be marked with two arrows in series. The arrows always point in the direction along the line towards an exit.

Light and gas signals for surface supplied dives
There are emergency signals usually associated with wet and closed bell diving by which the surface and bellman can exchange a limited amount of information which may be critical to the safety of the divers. They are for use when the voice communications system fails, and provide enough information that the bell can be recovered with minimal risk to the divers. These signals are not generally applicable to a diver who is supplied directly by umbilical from the surface, but if the umbilical is snagged and rope signals cannot be transmitted, these signals may be provided by hat light flashes and helmet flush (blowing gas from the helmet in a continuous stream by opening the or pressing the purge button).
 * Two light flashes at the bell means that the surface is not receiving voice communications from the bell. The bellman responds by blowing down bell gas twice, creating two large distinct eruptions of bubbles that will be seen at the surface, then recalls the diver and prepares for surfacing.
 * When the bell is ready to surface and the voice communications are not functioning, the bellman will blow down bell gas four times.
 * If there is a problem during the ascent, a long continuous blow-down is the signal to stop.

Miscellaneous emergency signals
Tap codes, made by knocking on the hull, are used to communicate with divers trapped in a sealed bell or the occupants of a submersible or submarine during a rescue.

A scuba diver who deploys a Delayed Surface Marker Buoy (DSMB) at the end of a dive may use a pre-arranged colour code to indicate to the surface support crew if there is a problem for which assistance is required. In some circles a yellow DSMB is considered an emergency signal, and red means OK. In most circles a second DSMB deployed on the same line will indicate a problem. A DSMB can also be used to carry up a slate with a message, but this is unlikely to be noticed unless a special arrangement has been made.

Other minor emergency signals include the use of mirrors, inflatable signal tubes, floating streamers, compressed air sirens, whistles and other noisemakers to alert the surface support personnel of a problem.

VHF radios and personal emergency locator beacons are available which can transmit a distress signal to nearby vessels and are pressure resistant to recreational diving depths, so they can be carried by a diver and activated at the surface if out of sight of the boat.

Flags
A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. Two styles of flag are in use. Internationally, the code flag "alpha", which has a white hoist and blue swallowtail fly, is used to signal that the vessel has a diver down and other vessels should keep well clear at slow speed. In North America a red flag with a white diagonal stripe from the upper left corner to the lower right corner is customarily used. The purpose of these flags is to notify other boats to steer clear for the safety of the divers and to avert the possibility of a collision with the dive boat which may be unable to maneuver out of the way.

Light and shape signals
A vessel supporting a diving operation may be unable to take avoiding action to prevent a collision, as it may be physically connected to divers in the water by lifelines or umbilicals, or may be maneuvering in the close proximity to divers, and is required to indicate this constraint by international maritime law, using the prescribed light and shape signals, and other vessels are obliged to keep clear, both for the safety of the divers, and to prevent collision with the diving support vessel. These signals and the rules for responding to them are specified in Rule 27 of the International Regulations for Preventing Collisions at Sea, also known as COLREGS, and "Rules of the Road", as quoted below.

A vessel restricted in her ability to manoeuvre, except a vessel engaged in mine-clearance operations, shall exhibit:
 * 1) three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
 * 2) three day shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;
 * 3) when making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in sub-paragraph 1;
 * 4) when at anchor, in addition to the lights or shapes prescribed in sub-paragraphs 1 and 2, the light, lights or shape prescribed in Rule 30.

A vessel engaged in dredging or underwater operations, when restricted in her ability to manoeuvre, shall exhibit the lights and shapes prescribed in sub-paragraphs (1, 2 and 3 above) of this Rule and shall in addition, when an obstruction exists, exhibit:
 * 1) two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists;
 * 2) two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass;
 * 3) when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shape prescribed in Rule 30.

Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (above) of this Rule, the following shall be exhibited:
 * 1) three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
 * 2) a rigid replica of the International Code flag "A" not less than 1 metre (3.3 ft) in height. Measures shall be taken to ensure its all-round visibility.

Surface marker buoys
Permanently buoyant or inflatable surface marker buoys may be used to identify and/or mark the presence of a diver below. These may be moored, as a shotline, and indicate the general area with divers, or tethered to one of the divers by a line, indicating the location of the group to people at the surface. This type of buoy is usually brightly coloured for visibility, and may be fitted with one of the diving flag signals. A surface marker buoy (SMB) tethered to a diver is usually towed on a thin line attached to a reel, spool or other device which allows the diver to control the line length to suit the depth, so that excessive slack line can be avoided.

A deployable, or delayed surface marker buoy (DSMB) is an inflatable marker which the diver inflates while underwater and sends up at the end of a line to indicate position, and usually either that he or she is ascending, or that there is a problem. The use of a DSMB is common when divers expect to do decompression stops away from a fixed reference, or will be surfacing in an area with boat traffic, or need to indicate their position to the dive boat or surface team. Divers can carry two differently coloured DSMBs so that they can signal to their surface support for help while decompressing underwater. By one system, a red buoy indicates normal decompression and a yellow buoy indicates a problem, such as shortage of gas, that the surface support should investigate and resolve. In other circles, two buoys of any colour on one line means the same.

A group of moored surface marker buoys may be used to demarcate an area in which diving is taking place. This is more likely to be used by commercial, scientific or public service divers to cordon off a work or search area, or an accident or crime scene.

Ultrasonic wearables
The Buddy-Watcher is a wrist mounted buddy alert device which sends an ultrasonic signal when a key is pressed, for at least 20 m through the water to the matching unit on the dive buddy, which will produce a silent vibratory and visual signal alerting the diver that their buddy wants attention. There is no direct indication to the sender whether the signal has been received and no indication of distance or direction to the buddy. The device is waterproof to 40 m, and therefore is suited for recreational scuba diving use, but not technical diving.

The UDI-28 and UDI-14 wrist mounted decompression computers have a communications feature between wrist units and a surface unit which includes distress signals, a limited set of text messages and a homing signal

Underwater messaging using smartphones and smartwatches
In 2022, University of Washington, developed a software app, AquaApp, for mobile devices that repurposes the microphones and speakers on existing smartphones and watches to enable underwater acoustic communication between divers. The software running on commodity Android smartphones placed in water-proof cases, supports sending one of 240 pre-set messages including SoS beacons and has a range of up to 100 metres.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Diver communications


text:
Ivano-Frankivsk Oblast

Ivano-Frankivsk Oblast (Івано-Франківська область), also referred to as Ivano-Frankivshchyna (Івано-Франківщина) or simply Frankivshchyna, is an oblast (region) in western Ukraine. Its administrative center is the city of Ivano-Frankivsk. It has a population of

The area, also known as Prykarpattia, was part of the historical region of Galicia, where the Kingdom of Galicia–Volhynia flourished. After World War I, the area became part of the Second Polish Republic and was administered as part of Stanisławów Voivodeship until the invasion of Poland. The area was annexed by the Soviet Union and was known as Stanislav Oblast until 1962, when its administrative center was renamed after the Ukrainian writer Ivan Franko. Kolomyia was a historical center of the oblast and remains a major cultural center of Pokuttia, the traditional name for the southern part of the oblast.

Name
On November 9, 1962, a decree was issued by the Presidium of the Verkhovna Rada of the UkrSSR, according to which: "Taking into account the wishes of the labor collectives of the city and region, the Presidium of the Verkhovna Rada of the USSR decided to rename the city of Stanislav (Stanislaviv) to Ivano-Frankivsk, and the Stanislav Oblast to Ivano-Frankivsk Oblast." The renaming was timed to the 300th anniversary of the city's founding and in honor of the outstanding Ukrainian writer Ivan Franko.

As with the rest of Ukraine's oblasts Ivano-Frankivsk may also be known by its matronymical name Ivano-Frankivshchyna (Івано-Франківщина). However, that name did not receive general public acceptance and commonly Ivano-Frankivsk Oblast is almost always called Prykarpattia (en. Prekarpathians) – a historic name for the same region. (Geographically the historic region covers a much larger portion of Ukraine than just the Ivano-Frankivsk region.) Formerly as Stanislavshchyna or Stanyslavivshchyna – Станіславщина, Станиславівщина.

Geography
Ivano-Frankivsk Oblast borders Lviv Oblast to its north and west, Zakarpattia Oblast to its south-west, has a 50-km long state border with Romania (Maramureș County) to its immediate south, and it borders Chernivtsi Oblast to the south-east and Ternopil Oblast to the east. It is situated partly in the Eastern European Plain and partly Carpathian Foothills. The oblast may be divided into three regions: mountainous, pre-mountainous, and plains.

The climate is mildly-continental and damp with cool summers and mild winters. The average monthly temperature in June is 18 C with 12 to 16 C in the mountains. The average monthly temperature in January is -4 C with -6 C in the mountains. Average precipitation varies annually around 650 mm with 1550 mm in the mountains.

Relief
The region is situated between two main regional tectonic plates: Carpathian fold belt and Volhynia-Podillya plate. The most prominent features of the first one are the Carpathian Mountains, while the second one - Dniester river.

The Carpathian Mountains contribute tremendously to the change in relief of Ivano-Frankivsk Oblast and their elevation rises from north-east to south-west stretching along the oblast's south-western border. The elevation of the oblast varies from 230 m (755 ft) to 2,061 m (6,762 ft) above sea level. The mountains occupy almost one half of the whole Oblast and consist of two main mountain ranges: the Gorgany (highest peak – Mt. Syvulia Major (1,836 m / 6024 ft)) and the Chornohora range (highest peak – Mt. Hoverla (2,061 m / 6,762 ft).

The rest of Ivano-Frankivsk Oblast is located within the Dniester river and Prut river valleys. The plains of the oblast are part of the Carpathian Foothills and Opillia Upland (part of Podillia Upland) which are cut through by Dniester. The upland has a temperate-climate habitat mixed with grassland and woodland – also known as the forest steppe. The relief of the region consists mostly of rolling hills of 230-400 m (755-1312 ft) over the sea level. Near river valleys are common canyons and ravines.

A particular feature of the southern region of the Ivano-Frankivsk Oblast is Stanislav Canyon, in the so-called Kherson Mountains, a deep cut in the local topography where episodic water flowing into the Baltic has steeply eroded a canyon formation.

The Dniester flows mainly through the Halych Raion and along the administrative border between Ivano-Frankivsk and Ternopil Oblasts. The territory of the region within immediate proximity to the river is traditionally known as Opillia. Opillia, however, stretches far beyond the oblast and only covers two of its raions: Halych Raion and Rohatyn Raion, both located in the north. Relief in the area consists of rolling hills uplands.

The Carpathian foothills consist mostly of low denudation accumulative uplands, while the right bank of Dniester along the border with the Ternopil Oblast depicts karst type relief of Pokuttia Upland. Because of it near that area along Dniester relief shows forms of canyon. Pokuttia Upland between Bystrytsia of Nadvirna and Prut River (Prut-Bystrytsia Upland) serves as drainage divide within the oblast between Dniester and Prut. Carpathian foothills have two depressions: one is at the confluence of Bystrytsia Solotvynska, Bystrytsia Nadvirnianska, Vorona and Bystrytsia rivers, called Bystrytsia Depression, and another is around the city of Kalush, called Kalush Depression.

Hydrology
Ivano-Frankivsk Oblast has a plethora of rivers, waterfalls, mountainous brooks, and smaller ponds, but there is almost no other type of bodies of water such as lakes and water reservoirs. Most of rivers either flow into Dniester or Prut River (tributary of Danube). The total water drainage area of the region is 13900 km². Segments of Dniester and Cheremosh River are used as administrative borders with Ternopil and Chernivtsi oblasts respectfully.

The water drainage divide between Dniester and Prut cuts the region through middle of following districts: Nadvirna Raion, Kolomyia Raion, Tlumach Raion, and Horodenka Raion.

Nature Sanctuaries
The region is a home to some 456 preserved areas (on June 1, 2006) of some 195,633 ha, 30 out of which are of all-national importance with an area of 108,742 ha and the rest of a local importance. In the Ivano-Frankivsk Region is located a strict nature reserve Gorgany that was created in 1996. There are five national parks in the region. There are numerous natural monuments of feature and habitat management areas (zakaznyks).

Government
The government in the region is headed by the chairman of the regional state administration (for simplicity sake - governor) appointed by the President of Ukraine. The governor appoints his deputies forming his regional governing cabinet to supervise the government policies in the region. Aside of the state administration the region has its own council that is headed by its chairman. The composition of the council depends on the popular vote in the region, while the chairman is elected within the elected council. Regional State Administration consists of the chairman and his deputies (5) supported by the "aparat" of the administration. Within the administration are numerous departments, each of them headed by a chief of department. The Ivano-Frankivsk Region State Administration has 17 departments and other government institutions such as the Children Service, regional state archives, and others.
 * Regional State Administration

 * Office of State Administration
 * Chief Department of Economy
 * Chief Financial Department
 * Chief Department industry and infrastructure development
 * Chief Department of tourism, Euro-integration, foreign relations, and investments
 * Chief Department of legal and interior policies
 * Chief Department of family, youth, and sports
 * Chief Department of labor and social security
 * Department of culture
 * Chief Department of agro-industrial development
 * Chief Department of regional development and construction
 * Department of communal management
 * Department of urban development and architecture
 * Chief Department of Education and Science
 * Chief Department of Health Security
 * Department of Extraordinary Situation and Protection of Population from Consequences of the Chornobyl Catastrophe
 * Media Department
 * Department of resources and management support
 * Children Service
 * Inspection of the State Technical Supervision
 * Inspection of quality and formation of resources of agricultural products
 * State Archives of the Region
 * Ivano-Frankivsk regional center for preparation and improving the qualification of workers of bodies of state power, bodies of local self-governing, state enterprises, institutions, and organizations
 * Regional council

 * Chairman: Oleksandr Sych (Svoboda)

Regional subdivisions
Since July 2020, Ivano-Frankivsk Oblast is administratively subdivided into six districts (raions).

Primary divisions (pre-reform)
The Ivano-Frankivsk Oblast was administratively subdivided into 14 districts (raions) as well as 6 cities (municipalities) which represented a separate raion and in direct subordination to the regional government, among which are Bolekhiv, Kalush, Kolomyia, Yaremche, and the administrative center of the region, Ivano-Frankivsk. Burshtyn became the 6th city of regional importance in 2014. The formation of the region was established in 1921 in the Second Polish Republic and was in majority preserved during the Soviet times. Most of the districts (former powiats) were reestablished as well in 1960s. The major industrial and cultural centers of the region were given a wider form of autonomy and assigned as the cities of regional subordination.

City municipalities (councils)/mayors
The oblast has 15 cities which are (alphabetical order): Bolekhiv, Burshtyn, Dolyna, Halych, Horodenka, Ivano-Frankivsk, Kalush, Kolomyia, Kosiv, Nadvirna, Rohatyn, Sniatyn, Tlumach, Tysmenytsia, and Yaremche. Five of those cities are of regional importance and the other ten are of district importance. All cities have its own council and mayor that represent a local form of self-government allowed by the laws on local administration and the Constitution of Ukraine. City municipalities of the region are independent from any district administration.

Town municipalities (councils)
Within the region there are 24 urbanized settlements (towns) which are a special settlement classification inherited from the Soviet municipal organization. Three of those towns serve as administrative centers of their respective districts. Each town has its own council that along with surrounding village councils compose a district administration which has its own executive branch, District State Administration, appointed by the President of Ukraine. Towns do not have a mayoral office and their head of the council serves as the main representative of the whole settlement.

Village municipalities (councils)
All other settlements in the region are considered rural and accounted for some 765 localities including villages and 20 selyshches (smaller villages) which are administered by 477 village councils. Some village municipalities consist of several villages, while others are a single-village municipality. There are several villages that are part of city municipalities such as Ivano-Frankivsk, Bolekhiv, and Yaremcha, while all others are spread out across the districts of the region.

Historical overview of subdivisions
When on November 27, 1939, the Soviet regime was established in Stanisławów Voivodeship, the Polish administrative division of it was kept almost the same until January 17, 1940. Only two powiats Stryj and Żydaczów were transferred away.

On December 4, 1939, the voivodeship was officially renamed into Stanislav Oblast. In 1940 the oblast was redivided into 37 raions and two municipalities (cities of oblast subordination). The administrative centers of the former raions were following settlements: Bohorodchany (town), Bolekhiv (city), Bilshivtsi (town), Bukachivtsi (village), Burshtyn (town), Voinylov (village), Vyhoda (village), Halych (town), Hvizdets (town), Horodenka (town), Delyatyn (town), Dolyna (city), Zhabie (village), Zhovten (town), Zabolotiv (town), Kalush (city), Kolomyia (city), Korshiv (village), Kosiv (city), Kuty (town), Lanchyn (town), Lysets (town), Nadvirna (city), Novytsya (village), Obertyn (town), Otynya (town), Pechenizhyn (town), Rohatyn (city), Rozhnyativ (town), Snyatyn (city), Solotvyn (town), Stanislav (city), Tlumach (city), Tysmenytsya (town), Chernelytsya (town), Yabluniv (town), Yaremcha (village). Two municipalities were cities of Stanislav and Kolomyia. On November 11, 1940, Delyatyn Raion was liquidated. On November 16, 1940, Novytsya Raion was re-administrated under town of Perehinske.

During the World War II the region was occupied by the Nazi Germany (see Operation Barbarossa). Along with Lviv, Drohobych and Tarnopil oblasts, it was reorganized on August 1, 1941, into Distrikt Galizien centered in Lemberg and annexed to the General Government. The area of the former Stanislav Oblast was divided into three kreis (counties): Kalusz, Stanislau, and Kolomea. On July 27, 1944, the region was liberated from the Nazi Germany by the Soviet Army (see Lvov–Sandomierz Offensive).

The administrative division of Stanislav Oblast was reinstated and confirmed on January 1, 1947, with the same 36 raions and two municipalities as their existed before the war. Several settlements, however, had their status elevated. The status of a town obtained Bukachivtsi, Vyhoda, and Yaremcha, while Halych and Horodenka became recognized as cities. The next major changes in the region took place in the late 1950s. In 1957 five raions were liquidated: Vyhoda, Zhovten, Kuty, Pechenizhyn, and Chernelytsia. Then another five were liquidated in 1959: Bukachivtsi, Korshiv, Perehinske, Solotvyn, and Stanislav. On December 30, 1962, within the oblast was created the Verkhovyna Industrial Raion, centered in a town of Verkhovyna.

On October 28, 1963, another major change took place when raions of the oblast were re-administered into the six rural raions, one – industrial, and two municipalities. There were the following administrative centers: Bohorodchany, Halych, Horodenka, Kalush, Kolomyia, Kosiv, Dolyna (municipalities – Ivano-Frankivsk (new name) and Kolomyia). On January 4, 1965, Dolyna Industrial Raion Raion was redesigned into the regular raion, while five other previous raions were recreated: Nadvirna, Rohatyn, Rozhniativ, Sniatyn, and Tlumach. On December 8, 1966, there were created Verkhovyna and Ivano-Frankivsk raions. That was the last major re-administration of the oblast.

On March 20, 1972, in the city of Kalush was created a municipality and it became a city of oblast subordination. On December 30, 1977, the same thing happened to Yaremcha status of which was elevated as well. On March 28, 1982, the Ivano-Frankivsk Raion was re-administrated under the Tysmenytsya Raion. On October 21, 1993, the city of Bolekhiv became of an oblast subordination with its own municipality. On December 14, 2006, Yaremcha was renamed into Yaremche.

Demographics
According to the Ukrainian Census of 2001 most of the population consider themselves Ukrainians with a small Russian diaspora mostly located within the city of Ivano-Frankivsk. The Russian language is the dominant foreign language in the region and well understood by everyone. Among other common foreign languages are Polish, English, and German languages. The population in the region as the rest of the country was on substantial decline.

Religion
The dominant religion in Ivano-Frankvisk Oblast is Ukrainian Greek Catholic Church, professed by 57% of the population. Another 35% is Eastern Orthodox and 6% are unaffiliated generic Christians. Adherents of Roman Catholic Church and Protestantism make up 1% of the population respectively.

Age structure

 * 0-14 years: 16.7% (male 118,518/female 112,130)
 * 15-64 years: 69.5% (male 468,589/female 489,596)
 * 65 years and over: 13.8% (male 63,324/female 126,635) (2013 official)

Median age

 * total: 37.3 years
 * male: 34.7 years
 * female: 40.0 years (2013 official)

Culture and tourism

Ivano-Frankivsk Oblast is home of numerous cultural festivals. There are numerous natural and architectural benchmarks that are scattered throughout the region.

One of the famous festivals is the Ukrainian International festival of ethnic music and land art "Sheshory" that usually takes place in the picturesque Hutsul village of the Kosiv Raion Sheshory since 2003. From 2007, however the festival has spread throughout the country taking place in Podolia, Kyiv Oblast, and other places. In August 2010 the village of Spas in the Kolomyia Raion hosted a culinary event Smachny Spas in association with "Sheshory", while in July of the same year another eco-cultural event Trypilske kolo in the Rzhyschiv city of Kyiv region.

The city of Ivano-Frankivsk hosts several other festivals such as the All-Ukrainian festival of art collectives "Carpathian Spring" that takes place every May. Every two year the festival of modern art "Impreza" takes place every other year. Every odd year the city hosts the festival national-patriotic music and poetry "Freedom". Since May 2001 every year the city of Ivano-Frankivsk is the capital of the European blacksmith movement hosting the "Festival of blacksmith" and the art exhibition "Ornamental Forging" that takes place at the Mickewicz Square and neighboring Andrii Sheptytsky Square in city's old town.

On the territory of Ivano-Frankivsk Oblast are located numerous monuments of architectural heritage. On February 8, 1994, near the city of Halych was established the National preserve of Ancient Halych. Among other important sites in the region is the Church of the Holy Spirit located in the city of Rohatyn as well as the Maniava Skete. Near the village of Maniava in Ivano-Frankivsk Raion. The oblast also accounts for some number of various wooden churches of Boykos and Hutsuls traditional architecture.

In the Kalush Raion (western part of the region) visitors can find the Carpathian Train that still uses a narrow gauge railway system. Train is used for its direct purpose transporting wood as well as for a tourist recreation. The biggest benchmark of the region is the Hoverla mountain, the tallest in the nation. However, due to increased touristic activities in the post-Soviet times the mountain is a subject to a high degree of pollution. No less interesting destination serve the Dovbush rocks that are located near the city of Bolekhiv in mountains. That location was a base of an anti-Polish Peasant movement. Near the Maniava Skete is located the highest waterfall in Ukraine, the Maniava waterfall (20 m). In the same Bohorodchany Raion visitors may find the local mud volcano located near the village of Starunia. It was noticed for the first time in 1977 after an earthquake that took place in Romania. Bukovel ski resort, centralized around the village of Polianytsia, on the ridge-lines of the Carpathian Mountain range at an elevation of 900 m represents a major all seasons tourist destination in the region. It is one of the most popular ski resorts in Eastern Europe and in 2012 was named the fastest growing ski resort in the world. Bukovel consists of 16 ski lifts with approximately 50 kilometers of pistes. As well as skiing visitors to the resort can enjoy 7 world class hotels, chalets with swimming pools and saunas, as well as numerous other recreational activities ranging from family friendly leisurely activities to extreme sports. During the warmer months the resort boasts cross-country and downhill mountain biking trails. Over 6,000 people visit the resort every year.

Historical and cultural sites

 * Recently, a monument of cultural heritage was erected in the city of Kolomyya in Pokuttya. The Pysanka Museum was built in 2000 and is the only museum dedicated to pyanskas in the world.
 * Another interesting historical site is the cavern complex in the Dovbush Rock. The site is dedicated to the legendary freedom fighter Oleksa Dovbush who in legend fights against the Polish szlachta. The rock complex is located about 7 mi south west from Bolekhiv near village of Bubnysche.
 * The Church of the Holy Spirit, built in 1598, is located in the north of the Oblast in the small city of Rohatyn.

Popular culture
In 1979 Sofia Rotaru performed the song "Krai" ([Native] Land) about Prykarpattia. In the song Rotaru calls Prykarpattia the land of the Cheremosh and Prut rivers.

State highways
Through Ivano-Frankivsk Oblast runs one European route which travels through the city of Rohatyn in the north. It coincides with the Ukrainian International highway which is the only highway of that classification in the region. The highway travels from Zhydachiv in Lviv Oblast and after passing Rohatyn travels towards Berezhany in Ternopil Oblast.

Besides that highway, through the region run three highways of national importance.
 * traveling from Lviv the route enters the region from the north near Rohatyn and after passesing the cities of Ivano-Frankivsk and Yaremcha continues on towards Rakhiv going over the Carpathian ridge.
 * starts in Stryi, passes through Ivano-Frankivsk, Kolomyia and Sniatyn, and continues on towards Chernivtsi.
 * starts from the center of Ivano-Frnkivsk and through Tysmenytsia (Ivano-Frankivsk Oblast) and Monastyryska (Ternopil Oblast), terminating in Ternopil.

There is also small network of minor P-highways.
 * runs from Tyaziv (north of Ivano-Frankivsk) through Tlumach and Horodenka to Sniatyn.
 * runs from Dolyna over the Carpathian to Khust (Zakarpattia Oblast).
 * runs from Tatariv (Yaremche municipality) to Verkhovyna, Kosiv, Kolomyia, Hvizdets, Horodenka, and Ternopil Oblast.
 * runs from Bohorodchany to the village of Stara Huta.
 * runs from Verkhniy Yaseniv (Verkhovyna Raion) to Usteriky, then by the Prut valley and the Chernivtsi Oblast border travels to Kuty where it turns into Chernivtsi Oblast towards Storozhynets.

Regional highways
T-network (09) includes:
 * - Kalush, Yasen, Kuzmynets
 * - Borshniv-Osada, Rozhniativ, Kosmach, Nadvirna
 * - Halych, Medukha, Zastavche, Pidhaitsi
 * - Ozeryany, Obertyn, Hvizdets, Zabolotiv, Rozhniv, Kuty
 * - Delyatyn, Lanchyn, Kolomyia
 * - Ivano-Frankivsk, Cherniiv, Nadvirna, Bystrytsia
 * - Kosiv, Rozhniv, Sniatyn
 * - Kalush, Burshtyn
 * - Bolekhiv, Tysiv, Kozakivka
 * - Pistyn, Mykytyntsi, Verkhniy Verbizh
 * - (Lviv Oblast) Kurovychi, Peremyshlyany, Rohatyn
 * - (Lviv Oblast) Kalush, Zhuravno, Zhydachiv, Rozdil, Mykolaiv
 * - (Chernivtsi Oblast) / (Romanian border) (route 209G) Seliatyn, Parkulyna, Dykhtynets, Marynychi, Pidzakharychi, Kuty, Sloboda Banyliv, Chortoryia, Hlynytsia, Chernivtsi
 * - (Chernivtsi Oblast) Horodenka, Khreshchatyk
 * - (Chernivtsi Oblast) Vyzhnytsia, Kuty, Pidzakharychi

Unique Tourist Attractions

 * Castles and fortresses
 * Pniv Castle
 * Chernylitsky Castle
 * Rakovet Castle
 * Galician castle

Notable people
People born in Prykarpattya include:

Historical figures
 * Yaroslav Osmomysl, prince of Halych
 * Roxelana, chief consort of Ottoman sultan Suleiman the Magnificent
 * Semen Vysochan, a leader of the Khmelnytsky Uprising beginning in 1648
 * Potocki family, Polish high nobles (magnates)
 * Józef Potocki, Great Hetman of the Crown
 * Oleksa Dovbush, 18th century folk hero
 * Stepan Bandera, Ukrainian independence activist
 * Dmytro Vitovsky, Austro-Hungarian and later Ukrainian separatist politician and military leader

Writers
 * Mariyka Pidhiryanka
 * Vasyl Stefanyk
 * Les Martovych
 * Ivan Vahylevych
 * Marko Cheremshyna
 * Manès Sperber

Artists
 * Sviatoslav Hordynsky, founder of the Association of Independent Ukrainian Artists
 * Mariia Stefiuk, opera singer
 * Mika Newton, singer
 * Dmytro Pavlychko, poet

title: Ivano-Frankivsk Oblast


text:
Lviv Oblast

Lviv Oblast (Львівська область, ), also referred to as Lvivshchyna (Львівщина, ), is an oblast in western Ukraine. The capital of the oblast is the city of Lviv. The current population is

Name
The region is named after the city of Lviv which was founded by Daniel of Galicia, the King of Ruthenia, in the 13th century, where it became the capital of Galicia-Volhynia. Daniel named the city after his son, Leo. During this time, the general region around Lviv was known as Red Ruthenia (Cherven' Rus'). Earlier, under Polish rule, the territory was part of the Cherven Cities.

Early history
The oblast strategic position at the heart of central Europe and as the gateway to the Carpathians has caused it to change hands many times over the centuries. In the Early Middle Ages, the territory was inhabited by the Lendians, an old Polish tribe. It was ruled variously by Great Moravia, Poland, Kievan Rus', the Kingdom of Galicia–Volhynia (circa 1200 to 1340; from 1246 under the suzerainty of the Golden Horde), and then ruled by the Kingdom of Poland and Polish–Lithuanian Commonwealth (1340 to 1772), the Austro-Hungarian Empire (1772 to 1918), West Ukrainian People's Republic and Poland (1919 to 1939), when it was part of the Lwów Voivodeship of the Second Republic of Poland. The region's historically dominant Ukrainian population declared the area to be a part of an independent West Ukrainian National Republic in November 1918 — June 1919, but this endured only briefly. Local autonomy was provided in international treaties but later on those were not honoured by the Polish government and the area experienced much ethnic tension between the Polish and Ukrainian population.

Establishment
The oblast was created as part of the Ukrainian Soviet Socialist Republic on 4 December 1939 following the Soviet invasion of eastern Poland and annexation of Eastern Galicia and Volhynia.

It was occupied by Nazi Germany from 1941 to 1944 following the start of Operation Barbarossa, where most of the local Jewish population were killed. Following the end of World War II, the region remained in Soviet hands as was arranged in the Tehran and Yalta conferences. Most local Poles were expelled and Ukrainians expelled from Poland arrived.

As a result of the 1951 Polish–Soviet territorial exchange the area of Belz passed from Poland to the Lviv Oblast, whereas the area of Ustrzyki Dolne passed from the Lviv Oblast to Poland.

In 1959, Drohobych Oblast was incorporated into Lviv Oblast.

Present day
Given its historical development, Lviv Oblast is one of the least Russified and Sovietized parts of Ukraine, with much of its Polish and Habsburg heritage still visible today.

In Ukraine today, there are three provinces (oblasts) that formed the eastern part of the Kingdom of Galicia and Lodomeria. Two of these, Lviv Oblast and Ivano-Frankivsk Oblast were entirely contained in the kingdom; the third oblast of Ternopil was mainly in the kingdom apart from four of its most northerly counties (raions). The counties of the Kingdom of Galicia remained largely unchanged when they were incorporated into successor states; with minor changes as detailed below, the current counties are almost co-extensive with those of the Kingdom.

During the 2014 Euromaidan protests, the region is also notable for having declared independence from the central government led by Viktor Yanukovych who started to use active military force against protestors. During Ukraine's decommunization process that accelerated after 2014, Lviv Oblast became the first region of Ukraine to remove all its Soviet-era monuments by January 2024.

Geography
The terrain of Lviv Oblast is highly varied. The southern part is occupied by the low Beskids mountain chains running parallel to each other from northwest to southeast and covered with secondary coniferous forests as part of the Eastern Carpathians; the highest point is Pikui (1408 m). North from there are the wide upper Dniester river valley and much smaller upper San River valley. These rivers have flat bottoms covered with alluvial deposits, and are susceptible to floods. Between these valleys and Beskyd lies the Precarpathian upland covered with deciduous forests, with well-known mineral spa resorts (see Truskavets, Morshyn). It's also the area of one of the earliest industrial petroleum and gas extraction. These deposits are all but depleted by now.

In the central part of the region lie Roztochchia, Opillia, and part of the Podolia uplands. Rich sulphur deposits were mined here during the Soviet era. Roztocze is densely forested, while Opillia and Podolia (being covered with loess on which fertile soils develop) are densely populated and mostly covered by arable land. In the central-north part of the region lies the Small Polesia lowland, geographically isolated from the rest of Polesia but with similar terrain and landscapes (flat plains with sandy fluvioglacial deposits and pine forests). The far North of the region lies on the Volhynia upland, which is also covered with loess; coal is mined in this area.

Climate
The climate of Lviv Oblast is moderately cool and humid. The average January temperatures range from -7 °C in the Carpathians to -3 C in the Dniester and San River valleys while in July the average temperatures are from 14 - 15 C in the Carpathians to 16 - 17 C in Roztochchia and 19 °C in the lower part of the Dniester valley. The average annual precipitation is 600 - 650 mm in the lowlands, 650 – in the highlands and up to 1000 mm in the Carpathians, with the majority of precipitation occurring in summer. Prolonged droughts are uncommon, while strong rainfalls can cause floods in river valleys. Severe winds during storms can also cause damage, especially in the highlands. The climate is favourable for the cultivation of sugar beets, winter wheat, flax, rye, cabbage, apples, and for dairy farming. It is still too cold to successfully cultivate maize, sunflower, grapes, melon, watermelon or peaches in Lviv Oblast. In the Carpathians conditions are favourable for Alpine skiing 3–4 months a year.

Governors

 * Chairmen of the Executive Committee

 * Representative of the President

 * Heads of the Administration

Subdivisions

Until the big district reform on July 18, 2020, Lviv Oblast was administratively subdivided into 20 raions (districts), as well as 9 city (municipalities) which are directly subordinate to the oblast government: Boryslav, Chervonohrad, Drohobych, Morshyn, Novyi Rozdil, Sambir, Stryi, Truskavets, and the administrative center of the oblast, Lviv.

On 18 July 2020, the number of districts was reduced to seven. These are:
 * 1) Chervonohrad Raion (Червоноградський район), the center is in the town of Chervonohrad;
 * 2) Drohobych Raion (Дрогобицький район), the center is in the town of Drohobych;
 * 3) Lviv Raion (Львівський район), the center is in the city of Lviv;
 * 4) Sambir Raion (Самбірський район), the center is in the town of Sambir;
 * 5) Stryi Raion (Стрийський район), the center is in the town of Stryi;
 * 6) Yavoriv Raion (Яворівський район), the center is in the town of Yavoriv;
 * 7) Zolochiv Raion (Золочівський район), the center is in the town of Zolochiv.

In addition, there are the city raions of the city of Lviv.

Demographics

 * Male/female ratio: 48%/52%
 * Nationalities (2001): 94.8% of the region's population are Ukrainians; 3.6% (or 92,600 people) are Russians; Poles account for 0.7%; there are also smaller German, Jewish and Romani minorities. Notably, the comparison of the 2001 Ukrainian census (mentioned above), with the last Soviet census of 1989 reveals that in those 12 years the number of Poles in the Lviv Oblast declined by 29.7 percent which, in the opinion of "Wspólnota Polska" Society defies explanation, and could possibly be attributed to the intensive Ukrainization of the Roman Catholic Church.

Age structure

 * 0-14 years: 15.7% (male 202,923/female 193,000)
 * 15-64 years: 70.0% (male 867,699/female 897,788)
 * 65 years and over: 14.3% (male 122,906/female 238,016) (2013 official)

Median age

 * total: 38.0 years
 * male: 35.2 years
 * female: 40.9 years (2013 official)

Religion
Fifty-nine percent of the religious organisations active in the Lviv Oblast adhere to the Ukrainian Greek Catholic Church. The Ukrainian Autocephalous Orthodox Church is the second largest religious body. The followers of the Latin Church and the Ukrainian Orthodox Church (Moscow Patriarchate) are mostly from the Polish, and Russian or non-Galician Ukrainian minorities respectively.

Historical and cultural sites
The city of Lviv contains a well-preserved main square (Rynok) and numerous historical churches. Other sites of interest are the historic Lychakiv Cemetery, the local museum of folklore, and the ruins of the famous Vysokyi Zamok. The name of the castle is closely tied to the name of the city. There is also a museum of military artifacts, the "Arsenal".

Well-preserved local wooden churches, castles, and monasteries can be found throughout the Oblast. One of them is the Olesko Castle which is first recorded in 1327. Another castle that was built at the end of the 15th century is Svirzh Castle in the village of Svirzh. One more and no less famous castle is the Pidhirtsi Castle. Its architectural complex consists of the three-story palace, Kostel, and small park. In Roztochia is also located the Krekhivsky monastery in the beech-pine grove at the foot of the Pobiina mount. The whole complex consists of the Saint Nicholas Church, the bell tower, numerous service structures, and defensive walls with towers. Another site worth of mentioning is the Tustan city-fortress which is built in the rock. The site was nominated as the historical and as the natural wonder of Ukraine. There also a nature complex in the valley of the Kamianka river in Stryi Raion. Another natural wonder of the region is the Kamin-Veleten (Rock-Giant in English) which is located near city of Pidkamin in Zolochiv Raion. The name of the local city means Under the Rock. A local museum of Ukrainian art and an institution of higher learning (Ivan Franko State University) are also present.

Economy
The most important research into cereal epidemics in the country is undertaken here. The National Academy of Agrarian Sciences of Ukraine's Institute of Agriculture in Obroshino is the center of study for cereal pathogens including powdery mildew of barley. In the early 2000s the most active researchers here were Olga Vronska and G. Kosilovich at the IoA. Puccinia recondita, Erysiphe graminis, (syn. Blumeria graminis) and various Pseudocercosporella spp. are present and are significant in winter wheat in this oblast.

Two introduced banded land snails, the Grove Snail (Cepaea nemoralis) and White-Lipped Snail (C. hortensis) are found here. C. n. was intentionally brought here in the late 1800s, but the genetic analysis of Gural-Sverlova et al., 2021 shows continued introductions have also occurred ever since. (The geographic distribution of both suggests they arrive through the gardening trade, as is known from other countries.) This analysis shows several distinct arrivals of C. n. yielding several present-day populations in and around Lviv.

Curiosities

 * In the 17th century, there were sizeable Scottish communities in Lviv and Brody.

title: Lviv Oblast


text:
Full-face diving mask

A full-face diving mask is a type of diving mask that seals the whole of the diver's face from the water and contains a mouthpiece, demand valve or constant flow gas supply that provides the diver with breathing gas. The full face mask has several functions: it lets the diver see clearly underwater, it provides the diver's face with some protection from cold and polluted water and from stings, such as from jellyfish or coral. It increases breathing security and provides a space for equipment that lets the diver communicate with the surface support team.

Full-face masks can be more secure than breathing from an independent mouthpiece; if the diver becomes unconscious or suffers an oxygen toxicity convulsion, the diver can continue to breathe from the mask, unlike a scuba mouthpiece which is normally gripped between the teeth.

Full-face diving masks are often used in professional diving. They are relatively rarely used in recreational diving.

Function
The full-face mask provides breathing gas to the diver, and an air space to facilitate underwater vision. There is usually one air space for both breathing and vision, and this is automatically equalised by the breathing gas during descent. However, some models have a mouthpiece isolating the breathing gas supply from the rest of the interior of the mask, or have a divided interior, and the main air space must then be equalised during descent by exhaling through the nose.

Most full-face masks have an open circuit demand gas supply, but free-flow and closed circuit applications also exist and models used in commercial diving may be normally demand supplied, but with a free-flow option selectable by the diver.

Positive pressure
For some applications it is desirable for the gas inside the mask or helmet to remain at a pressure slightly above ambient at all times while in the water, as this will prevent any contamination from leaking into the gas space during inhalation if the face or neck seal, or the exhaust valve system, does not seal perfectly. In clean water such a leak is a minor problem, but leaks of contaminated water can be a hazard to health, and even life-threatening. A positive pressure inside a free-flow helmet is easily achieved by slightly increasing the opening pressure of the exhaust valve, provided it is adjustable, but for a demand system the cracking pressure of the demand valve must also be adjusted, so that it delivers gas before the internal pressure drops below external ambient pressure. This is not difficult, as a slight adjustment to second stage valve spring pressure is all that is required. The problem is that when the mask or helmet is off the diver, and the gas supply is pressurised, the demand valve will leak continuously, and a large amount of gas can be lost. The Interspiro Divator Mk II mask has a second stage regulator which has a manual lock on the demand valve to prevent free-flow when the mask is not in use, which unlocks when a breath is taken, and must be reset when the mask is taken off.

Construction
A full-face mask consists of a transparent faceplate (lenses, or window) through which the diver can see, a connection to a source of breathing gas, a means of removing any water which may get inside, some facility for the diver to block the nose to equalise the ears, a means of sealing these components to the diver's face and preventing ingress of water and a means of securing the assembly to the diver's head. Additional components may include communications equipment, lights, alternative breathing gas connections, and a means to defog the interior surface of the faceplate.

Two basic configurations are in common use: Those with a soft elastomer skirt which seals around the periphery of the face, and those with a rigid frame supporting the other components, which is sealed to the face by a soft foam ring which is clamped to the frame by a metal band, to which the straps are secured (band mask)

Faceplate or lenses
The faceplate, viewport, or lens is a transparent window, usually flat, which encloses an air space in front of the diver's eyes and allows the eyes to focus correctly underwater. Several shapes have been used for faceplates and lenses:
 * Circular, as in WWII Italian frogman's rebreathers and in some early British frogman's rebreathers.
 * Oval, in some early British frogman's rebreathers.
 * Triangular with rounded corners, in some Siebe Gorman fullface masks intended for use with an aqualung set, and in the "Jack Browne" band masks made by DESCO for rebreather, open circuit demand, and free-flow applications.
 * Some of DESCO's fullface mask windows were egg-shaped (wider above).
 * Rectangular with the ends of the sides bent back for better sideways visibility, as in the Admiralty Pattern full-face mask made by Siebe Gorman and used on the Siebe Gorman CDBA.
 * In some older masks, small separate lenses, like some gasmasks.
 * Kidney shaped, as in the Cressi full-face mask, or approximately rectangular, with a deep cut-out for the nose pocket, as in the KM-48.

The shape and maximum size of mask and helmet viewports changed with availability of tougher and easily moulded transparent synthetic materials: Clear acrylic (perspex) became available in 1933 and polycarbonate in 1958. Diving helmet windows had been of glass for a long time, but a rigid helmet supported by the corselet resting on the shoulders can carry glass much thicker, stronger, and heavier than a mask strapped over the face and supported by the neck.

Frame
A structural component is needed to connect all the working parts together and hold the mask in shape. Most full-face masks use a rigid frame for this purpose, which directly or indirectly connects the components together and holds the assembly in shape (Kirby Morgan Exo, Supermask and bandmasks, John Browne mask). The rubber moulding which incorporates the skirt seal may also be sufficiently stiff in places to partially perform this function (Cressi-sub, Scubapro), and the faceplate may also be structural (Dräger Panorama, Ocean Reef Neptune, Aga Divator).

Face seal
The frame supporting the functional components must be sealed around the face to maintain a leak free internal air space over the eyes, nose, and mouth. Two methods are used.

Soft skirt
The soft skirted full-face mask is the more common arrangement, and is generally considerably lighter and more compact than the more sturdy and rigid band masks. There is usually a plastic frame which supports the faceplate (or lenses) and a demand valve, but in some cases the lenses and demand valve or rebreather mouthpiece may be attached independently to the rubber mask structure, which is integral with the skirt.

Band-masks
Band-masks generally have a single faceplate, which may be relatively large, firmly mounted to a rigid frame which also holds the demand valve or other gas supply components. The frame may be of metal (often brass), a strong engineering plastic, or a fibre reinforced resin composite. A face seal and in some cases a neoprene hood is clamped on by the metal band, which may have several buttons protruding, onto which the straps of the spider are fastened to secure the mask to the diver's head. Where a hood is included, it may have a zipper up the back for ease of fitting, and the spider is secured over the hood. A band mask is generally heavier and more cumbersome to fit than a soft skirted mask, and is not as easily fitted without assistance. It provides greater security and protection to the diver than a soft-skirted full-face mask, and is lighter and quicker to fit than a helmet. Most band-masks are fitted with demand systems for gas supply, but can be operated in free-flow mode.

Straps
A system of three to five straps is used to secure the mask to the diver's head. This component is often referred to as the spider. It is usually a rubber component comprising a group of straps radiating from a central patch or ring, which rests against the back of the diver's head, low enough to resist slipping off over the top. The straps may pass through quick-adjust buckles attached to the mask skirt, or may have holes to hook onto the buttons of a band mask. This strap system is more secure than a single double-ended half-mask strap, however, a full-face mask is far more difficult to replace underwater, if dislodged, than a half-mask.

Internal layout
Four types of internal layout can be distinguished.

Open plan
The simplest arrangement is a single interior space, with no subdivisions, and no mouthpiece. This is most appropriate to free flow systems. In this arrangement the diver can talk clearly, including talking with other divers underwater. This allows communications equipment (usually an intercom wire or by modulated ultrasound) to be installed in the mask and is very useful for working divers. If an open plan full-face mask floods underwater, it can be more difficult to clear than with a mouthpiece.

There also is the problem of "dead space" inside some masks causing risk of carbon dioxide retention. Free flow air supply overcomes these problems by providing so much air that the mask is constantly flushed. The cost is high noise level and very inefficient air usage on some models.

Internal oro-nasal breathing mask
With a small (oro-nasal) breathing mask enclosing the mouth and nose inside the full-face mask, the dead space is considerably reduced, but the smaller space around the mouth increases the distortion of speech.

Internal mouthpiece
A mouthpiece with bite-grip connects the gas supply directly to the diver's mouth inside the mask. If the mask floods, the diver can continue to breathe while clearing the mask, and it minimises dead space. Many Royal Navy and frogman's rebreathers have this mask arrangement. It makes clear talking difficult, but not impossible. For many years British armed forces divers used the Admiralty Pattern full face mask, with a long rectangular window, largely flat, and bent back 90° at the ends, as in the illustration of a diver with a CDBA rebreather. The lower skirt has a hole that a breathing set mouthpiece is fitted through.

Mouthpiece on a detachable pod
Kirby-Morgan makes a unique configuration of full-face mask, the KM-48 Supermask, which has some characteristics of a half mask, while retaining many of the advantages of the full face mask: The rigid plastic main frame of the mask has a rubber skirt which seals around the eyes and nose like a standard half-mask, the nose may be pinched through the rubber nose pocket to equalize in the same way as with a half mask, and there is an extension to the skirt which seals around the lower part of the face and encloses the mouth. This mask has a clip-on pod section which carries the demand valve, and this part seals against the lower part of the frame, allowing the diver to remove the regulator pod when on the surface, or to use an alternative gas supply, which can either be mounted on another pod, or be an ordinary Scuba regulator second stage with a standard mouthpiece. This feature makes it possible to use bailout gas supplied by a dive buddy with a standard regulator while wearing a Supermask. An optional pod with a dive/surface valve for use with rebreathers is available to military users.

Attachment of breathing gas supply components
Demand valve, twin hoses, rebreather mouthpiece or free-flow air supply hose may connect to the mask in various ways, including:-
 * Connection of surface supply and bailout hoses to a bailout block on the mask frame, typically at the right temple. From there integral plumbing takes the air to the integral demand valve and free-flow/defog port.
 * Demand valve rigidly connected to the lower part of the frame, with external bailout block.
 * Demand valve or rebreather mouthpiece plugged into the lower part of the frame.
 * Demand valve plugged into a port on the side of the lower part of the frame (for bailout).
 * Twin hoses ported through the lower part of the window, as in the Siebe Gorman aqualunger's full-face mask.
 * Through the mask's flexible skirt at the bottom, as with Siebe Gorman frogman's masks, for example the Siebe Gorman CDBA.
 * The early DESCO full-face mask's twin breathing hoses entered through the skirt at the sides, level with the lower end of the nose, pointing backwards and a bit downwards, to keep the breathing tubes shorter to reduce the risk of snagging.

Fitting
The full-face mask is generally the last piece of equipment fitted before the dive, as it is cumbersome and makes fitting other equipment more difficult by restricting the diver's field of vision, and the mobility of the head. The fitting may require the help of an attendant, particularly for the heavier band masks. The straps must be tensioned sufficiently to ensure a good seal, and to hold the mask securely to the diver's head, but not so tight as to cause discomfort during the dive. It is possible to adjust the fit to some extent during the dive.

Clearing
Water which enters the air spaces of the mask may be expelled either under the lower edge of the skirt, or through the exhaust port of the demand valve, or through a drain valve fitted for this purpose.

Equalising
The full-face mask must provide a means for the diver to block the nostrils for equalizing the middle ears. This may be provided in several ways. Some masks have a soft rubber nose pocket which allows the diver to pinch the nose directly, some have a soft cushion which can be pressed against the lower part of the nose to occlude the nostrils, and others have a mechanism which applies soft levers to the sides of the nose to pinch it in the same way that it would be done with fingers. The details of these mechanisms varies, but they all work. Some need to be adjusted to suit the individual diver, others are sufficiently flexible to fit almost anyone.

Defogging
Most full-face masks do not have fresh airflow directly over the interior of the faceplate, and are to some extent susceptible to fogging by condensation during a dive. This may be minimized by application of a demister surfactant before the dive, by rinsing during the dive, or in those cases where the system allows, by purging the mask through a free-flow/defog valve, which directs a flow of dry air over the inner surface of the faceplate. This facility uses a lot of air, and is usually only available on models intended primarily for surface supplied applications.

Some British Army and Russian gas masks are designed so that when the wearer breathes in, the inflow of air blows over the inside of the mask window and tends to evaporate any mist deposit on it. This feature is also found on the original Kirby Morgan EXO-26 mask, but the later EXO-BR uses an oro-nasal inner mask to reduce dead space.

Surface breathing
Full-face masks intended for use with scuba may provide a method of switching to atmospheric air when above the surface, to save breathing gas. Rebreather systems often incorporate a dive/surface valve in the mouthpiece which may provide an opening to the ambient environment when the loop is isolated. Some other full-face masks allow the demand valve to be unplugged on the surface, or provide a "snorkel valve" port which can be opened to allow atmospheric air to enter. The small saving on breathing gas is unimportant with surface-supplied breathing apparatus.

Bailout
Emergency provision of an alternative breathing gas source is required in case of a failure of the primary gas supply. This is managed in several ways by full face masks.

The most prevalent method for masks intended for surface supply applications is known as a bailout valve. The surface supplied diver generally carries a bailout gas supply sufficient to reach a place of safety based on the planned dive profile. This gas supply is regulated by a scuba first stage regulator, and plumbed into the primary air supply circuit via a bailout valve before it reaches the demand valve. The full face masks designed for surface supply work usually mount this valve on the side of the mask frame, in the bailout block, where it is convenient and easily reached by the diver. The bailout cylinder valve is normally open during the dive. To switch to bailout, the diver simply opens the bailout valve, and is immediately supplied by gas from the bailout cylinder.

A similar functionality can be provided for masks without an integral bailout block, by mounting an external bailout block at a convenient place on the diver's harness. Surface supply and bailout supply hoses are connected to this block, which works exactly the same way as the integral block. The same method can be used for open circuit scuba diving, but this only allows for a single gas switch. Gas manifolds with more than two gas supply options are technically possible, but allow for a wider range of operator error and are therefore considered high risk, as the consequences of switching to a gas unsuitable for the current depth may be fatal. This system does not allow for supply of bailout gas to another diver. This system is used for most full face masks, as they have no other option. Surface supplied divers use the pneumofathometer hose to supply gas to another diver.

Rebreather systems which use a bailout valve on the mouthpiece are often the method of choice for use with full-face masks, as the bailout mechanism is provided in the mouthpiece, and works the same whether used with a full-face mask or a half mask.

A few models of full-face mask are provided with secondary ports to which additional demand valves can be connected, either by screw connector (Ocean Reef) or by bayonet style connector (Dräger). These allow for bailout or decompression gas to be ported to the mask via an entirely independent scuba set, but it is necessary to control which gas is used at any given time by using a valve on the supply line or cylinder. The Dräger Panorama mask also allows the primary demand valve to be unplugged from the mask and a bailout demand valve to be substituted. This can be done underwater with very little water ingress to the mask, and is closely equivalent to switching demand valves with a half mask, but a little slower and more complex.

The Kirby-Morgan KM 48 Supermask is unique, in that the airspace for the eyes is completely separate from the mouth area, and the mask can be worn as a half mask by leaving off the mouthpiece pod, which holds the demand valve or rebreather mouthpiece. This allows bailout to a standard scuba demand valve with mouth grip, but also allows the diver to carry bailout gas fitted to a second pod, which can be clopped to the mask when the primary pod has been unclipped. This can be done underwater, and as there is a standard mouthpiece inside the pod, breathing can commence before the pod is fully connected and sealed. The pod can be cleared of water after sealing, and the eye-space is not affected by the switch. A final alternative sometimes used by recreational divers, is to bail out to a standard demand valve by removing the full face mask completely, and then fitting a backup half mask.

Safety
It may take a fairly long time to remove the mask to switch to breathing from the atmosphere. To avoid this, some full-face masks have a valve to switch between breathing from the set and breathing from atmosphere. The 'dive/surface valve', or 'snorkel valve', should be easily operated by the diver, even if wearing thick diving gloves, but not projecting so far that it can be easily knocked against things in low visibility water or in the dark, or in hand-to-hand combat underwater.

A full-face mask provides better security of breathing gas supply than a half-mask if there is a risk of the diver losing consciousness underwater.

The mask faceplate is generally a high impact strength polymer which is securely attached to the skirt or frame. A failure of the faceplate can be a life-threatening incident with some full face masks, as the water will flood into the oro-nasal inner mask and compromise the air supply. This problem is avoided by the masks which include a mouthpiece.

Not all divers will get a satisfactory seal from the skirt of any given full-face mask, as face shapes and sizes differ, but most divers will be able to find a mask that works for them. A major flood caused by a temporarily dislodged mask is easily drained by purging after replacing it in the correct position, and adjusting the straps if necessary. Lesser leaks will usually drain automatically from the mask through the exhaust valve of the demand valve or a purge valve fitted for that purpose as long as the mask is orientated with the valve at the low point. If there is too much water in the mask to allow inhalation it can usually be cleared using the purge button on the demand valve.

History
A full face diving mask was invented by Yves le Prieur in 1933.

The free-flow type of full-face mask is also sometimes referred to as a Jack Browne rig, named for a DESCO engineer who designed an early version of a full-face mask with a surface-supplied free-flow air supply.

title: Full-face diving mask