Diving hazards and precautions

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Diving hazards and precautions

Divers face specific physical and health

Health

In 1948, the World Health Organisation defined health as ?a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.? ...
risk

Risk

Risk is a concept that denotes the precise probability of specific eventualities. Technically, the notion of risk is independent from the notion of value and, as such, eventualities may have both beneficial and adverse consequences....
s when they go underwater

Underwater

Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river....
(e.g. with scuba

Scuba set

A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving....
or other diving equipment

Diving equipment

The fundamental item of diving equipment used by divers is the Scuba sets, such as the Aqua-Lung or Rebreather. There are other important pieces of equipment that make diving safer, more convenient or more efficient....
) or use high pressure breathing gas

Breathing gas

Air is the most common and only natural breathing gas. Other artificial gases, either pure gases or mixtures of gases, are used in breathing equipment and enclosed habitats such as Scuba set, surface supplied diving equipment, recompression chambers, submarines, space suits, spacecraft and anaesthetic machines....
es. Some of these conditions also affect people who work in raised pressure environments out of water, e.g. in caisson

Caisson (engineering)

In geotechnical engineering, a caisson is a retaining, watertight structure used, for example, to work on the foundation of a bridge pier , for the construction of a concrete dam, or for the repair of ships....
s.

k on the boldface links for more information about each topic. cellspacing="0" border="1" bgcolor="white">

Need to:

Remedy

Comments

Breathe underwater

Open-circuit scuba set
Scuba set

A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving....

Easy to refill.

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Encyclopedia

Divers face specific physical and health

Health

In 1948, the World Health Organisation defined health as ?a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.? ...
risk

Risk

Underwater

Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river....
(e.g. with scuba

Scuba set

A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving....
or other diving equipment

Diving equipment

Breathing gas

Caisson (engineering)

The ordinary features of diving

Click on the boldface links for more information about each topic.

Need to:	Remedy	Comments
Breathe underwater	Open-circuit scuba set Scuba set A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving....	Easy to refill. Safer to use than a rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... .
	Rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere....	Longer duration per weight of set, but needs more training to be safe.
	Surface supplied diving Surface supplied diving Surface supplied diving refers to diving activities using equipment supplied with breathing gas using an Umbilical cord#Other uses for the term "umbilical cord" from the surface, often from a diving support vessel but possibly, indirectly via a diving chamber....	Mostly for work diving
	Standard diving dress Standard diving dress A standard diving dress consists of a metallic diving helmet, an airline or air hose from a surface supplied diving air diving pump, a canvas diving suit, diving knife and boots....	Mostly for work diving. Mostly merely of historical interest now.
	Liquid breathing Liquid breathing Liquid breathing is a postulated form of Respiration in which a normally air-breathing organism breathes an oxygen-rich liquid , rather than breathing air.... system	(In the real world this is at the early experiment stage. It should allow very deep diving when it is developed.)
See underwater. Protect the eyes. (The human eye Eye Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.... cannot focus Focus (optics) In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge .... accurately when directly submerged.)	Eyes-and-nose diving mask Diving mask A diving mask is an item of diving equipment that allows scuba diving, free-diving, and snorkeling to see clearly underwater. When the human eye is in direct contact with water as opposed to air, its normal environment, light entering the eye is refracted by a different angle and the eye is unable to Focus the light....	Easy to clear if flooded. Easily knocked off.
	Full face mask	Allows talking if no mouthpiece inside. Difficult or impossible to go to snorkel on running out of air.
	Diving helmet Diving helmet File:Kask-nurka.jpgDiving helmets are worn mainly by professional diving engaged in surface supplied diving, though many models can be adapted for use with SCUBA equipment....	As fullface mask. Protects the head well.
	Special contact lens Contact lens A contact lens is a corrective lens, cosmetics, or therapeutic lens usually placed on the cornea of the eye. Modern soft contact lenses were invented by the Czech Republic chemists Otto Wichterle and Drahoslav L?m, who also invented the first gel used for their production.... es	Occasionally used by commando frogmen instead, to avoid searchlight beams reflecting off a mask window.
Move faster than with unequipped swimming	Fins Swimfin Swimfins, swim fins, shinfin fins or flippers are worn on the foot or leg and made from finlike rubber or plastic, to aid movement through the water in Water sport activities such as swimming, bodyboarding, bodysurfing, kneeboarding , riverboarding, and various types of underwater diving.... on feet	Cheap, easy to use. Even without a diving suit, wetsuit bootees let the diver wear bigger fins.
Move faster than with unequipped swimming	Diver Propulsion Vehicle Diver Propulsion Vehicle A Diver Propulsion Vehicle or a DPV is an item of diving equipment used by Scuba diving divers to increase their range while underwater where their endurance is restricted due to limited availability of breathing gas and need to avoid decompression sickness.... s	Faster but expensive, and heavy and bulky to carry about on land. Also makes it easier to lose track of where he is.
Avoid hypothermia Hypothermia Hypothermia is a condition in which an organism's temperature drops below that required for normal metabolism and bodily functions. In warm-blooded animals, core body temperature is maintained near a constant level through biologic homeostasis.... (losing body heat to the water)	In cool or cold water, wear an adequately warm diving suit Diving suit A diving suit is a garment or device designed to protect a diver from the underwater environment. Modern diving suits can be divided into two kinds:... for the conditions.	Much heat can be lost from a head without a hood.
Control buoyancy Buoyancy In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body....	Diving weighting system Diving weighting system Divers wear weighting systems, weight belts or weights, generally made of lead, to counteract the buoyancy of other diving equipment, such as diving suits and aluminium diving cylinders.... s	Usually a weight belt. Some breathing sets have built-in weight pouches.
	Diving suit Diving suit A diving suit is a garment or device designed to protect a diver from the underwater environment. Modern diving suits can be divided into two kinds:... s	The buoyancy of most drysuits can be changed during the dive.
	Buoyancy compensators	These make diver's buoyancy control much easier.
Protect the skin from cuts and stings and grazes	Diving suit Diving suit A diving suit is a garment or device designed to protect a diver from the underwater environment. Modern diving suits can be divided into two kinds:... s and diving gloves and diving suit bootees serve this purpose.	In very warm water try diving in a boiler suit, or other strong clothes with long sleeves and legs.
Breathe from atmosphere to save air when on surface	Snorkel	Advisable, despite some naval divers' opinions.

Effects of relying on breathing equipment while underwater

Being unable to breathe fresh air naturally whilst submerged and relying on limited breathing gas supplies and fallible breathing equipment can have these effects. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
Type	Cause	How to avoid it
Drowning Drowning Drowning is death from suffocation caused by a liquid entering the lungs and preventing the absorption of oxygen leading to cerebral Hypoxia and cardiac arrest....	Being unable to inhale anything but water	See under "anoxia" hereinunder
Secondary drowning	Can occur hours after a near drowning	Prompt medical treatment after near drowning
Oxygen toxicity Oxygen toxicity Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen at elevated partial pressures. It is also known as oxygen toxicity syndrome, oxygen intoxication, hyperoxia, or the Paul Bert effect and Lorrain Smith effect, after the researchers who pioneered its discovery and desc...	Breathing gas at too high a partial pressure Partial pressure In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.... of oxygen Oxygen Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]... ; partial pressure depends upon proportion of oxygen and depth	Proper training before using a rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... or oxygen Oxygen Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]... enriched gases such as nitrox.
Hypoxia Hypoxia (medical) Hypoxia is a Pathology condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise.... or anoxia Anoxia The term anoxia means a total decrease in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:... occurs while having gas to breathe, but where the oxygen partial pressure Partial pressure In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.... is too low to sustain normal activity or consciousness.	A faulty or misused rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... can provide the diver with hypoxic gas	Keep rebreathers properly maintained. Proper training before using a rebreather.
	Some deep diving breathing gas Breathing gas Air is the most common and only natural breathing gas. Other artificial gases, either pure gases or mixtures of gases, are used in breathing equipment and enclosed habitats such as Scuba set, surface supplied diving equipment, recompression chambers, submarines, space suits, spacecraft and anaesthetic machines.... es such as trimix Trimix Trimix is a breathing gas, consisting of oxygen, helium and nitrogen, and is often used in deep commercial diving and during the deep phase of dives carried out using technical diving techniques.... and heliox Heliox Heliox is a breathing gas composed of a mixture of helium and oxygen .Heliox has been used medically since the 1930s, and although the medical community adopted it initially to alleviate symptoms of upper airway obstruction, its range of medical uses has since expanded greatly, mostly because of the low density of the gas.... can be hypoxic	Don't breathe hypoxic gas in shallow water. Proper training before using mixed gases.
	A full cylinder standing for a long time while the inside of the cylinder rust Rust Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture.... s, using up oxygen in the contained air, before the diver uses the cylinder	Keep cylinders routinely checked and tested. If a cylinder has stood full for months, empty it and refill it.
Anoxia Anoxia The term anoxia means a total decrease in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:... due to having no air or gas to breathe	Equipment failure - particularly in rebreathers that monitor and maintain oxygen content	Keep equipment routinely checked and in good condition
	Running out of air due to poor dive discipline	Better training of divers. More disciplined attitude when underwater.
	Running out of air due to getting trapped by nets	Better awareness underwater. Carry a diver's net cutter, or dive tool/knife Diving equipment The fundamental item of diving equipment used by divers is the Scuba sets, such as the Aqua-Lung or Rebreather. There are other important pieces of equipment that make diving safer, more convenient or more efficient.... .
	Running out of air due to getting trapped or lost in enclosed spaces underwater (e.g. cave Cave A cave is a natural underground void large enough for a human to enter. Some people suggest that the term cave should only apply to cavities that have some part that does not receive daylight; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and grottos.... s and shipwrecks)	Specific training and leadership for such types of diving. See cave diving Cave diving Cave diving is a type of technical diving in which specialized Scuba set is used to enable the exploration of natural or artificial caves which are at least partially filled with water.... and wreck diving Wreck diving Wreck diving is a type of recreational diving where shipwrecks are explored. Although most wreck dive sites are at shipwrecks, there is an increasing trend to Sinking ships for wreck diving sites.... .
	Running out of air due to getting lost in open water	Better training and leadership, including in using a compass Compass A compass, magnetic compass or mariner's compass is a navigational instrument for determining direction relative to the earth's magnetic poles.... underwater
Salt water aspiration syndrome Salt water aspiration syndrome Salt water aspiration syndrome is a rare diving disorders suffered by Scuba diving who inhale a mist of seawater from a faulty demand valve causing irritation of the lungs....	Inhaling a mist of sea water from a faulty demand valve causing a reaction in the lung Lung The lung is the essential respiration organ in air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located in the chest on either side of the heart.... s	Keep equipment routinely checked and in good condition
Carbon monoxide poisoning Carbon monoxide poisoning Carbon monoxide poisoning occurs after the inhalation of carbon monoxide gas. Carbon monoxide is a product of combustion of organic matter under conditions of restricted oxygen supply, which prevents complete oxidation to carbon dioxide ....	Air cylinder filled by a compressor which sucked in products of combustion Combustion Combustion or burning is a complex sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering.... , often its own engine's exhaust Exhaust Exhaust or exhaustion may refer to:...	Proper precautions when filling cylinders
	Oil getting into the air feed and firing in the air compression cylinder, like in a diesel Diesel Diesel or diesel fuel in general is any fuel used in diesel engines. The most common is a specific fractional distillation of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid or gas to liquid diesel, are increasingly being developed and adopted.... engine	Proper servicing of the compressor
Emphysema Emphysema Emphysema is a chronic obstructive pulmonary disease . It is often caused by exposure to toxin Chemical substance, including long-term exposure to tobacco smoking.... caused by inhaling oil mist	This happens gradually over a long time. This is a particular risk with a pumped surface air feed.	Use proper filters in the air pump or air compressor.
Carbon dioxide poisoning: hypercapnia Hypercapnia Hypercapnia or hypercapnea , also known as hypercarbia, is a condition where there is too much carbon dioxide in the blood. Carbon dioxide is a gaseous product of the human body metabolism and is normally expelled through the lungs....	Re-inhaling carbon dioxide Carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.... -laden exhaled gas	Minimise the volume of any enclosed spaces which the diver breathes through. For example, this hazard can happen with diving with a large "bubblehead" helmet.
	With a rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... , the diver re-inhales carbon dioxide Carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.... because the soda lime Soda lime Soda lime is a mixture of chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent CO%E2%82%82_retention and carbon dioxide poisoning.... scrubber cannot absorb the exhaled carbon dioxide as fast as the diver produces it. See Rebreather#Carbon dioxide scrubber Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... .	British naval divers called it shallow water blackout Shallow water blackout A shallow water blackout is a Unconsciousness caused by cerebral hypoxia towards the end of a Apnea dive in water typically shallower than five metres , when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it.... . Keep rebreathers properly maintained. Proper training before using a rebreather.
Various effects of breathing a wrong gas	A wrong gas was put in a cylinder	Check conditions where you have your cylinders refilled. Put the proper gas identification markings on cylinders.

Effects of barotrauma or pressure damage

See barotrauma

Barotrauma

Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid....
and pressure

Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
for more information.

On descent

Air spaces within the body provide no support against greater outside pressure. This can happen from losing control of buoyancy

Buoyancy

In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body....
causing excessive vertical speed during descent. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
Type	Cause	How to avoid it
Eardrum Eardrum The tympanic membrane , is a thin biological membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear.... damage. Cold water in the middle ear Middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear.... chills the inner ear Ear The ear is the sense organ that detects sounds. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species.... , causing dizziness Dizziness Dizziness describes a number of subjective symptoms, which the patient may describe as feelings of lightheadedness, floating, wooziness, giddiness, confusion, disorientation or loss of balance.... and disorientation etc.	Failing to equalize the pressure in the middle ear Middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear.... with surrounding pressure.	Do not dive if the eustachian tube Eustachian tube The Eustachian tube is a tube that links the pharynx to the middle ear. In adults the Eustachian tube is approximately 35 mm long. It is named after the sixteenth century anatomist Bartolomeo Eustachi.... is congested, e.g. with the common cold Common cold Acute viral rhinopharyngitis, or acute coryza, usually known as the common cold, is a highly contagious, virus infectious disease of the upper respiratory system, primarily caused by picornaviruses or coronaviruses.... . Proper diver training in clearing the ears.
	The pressure in the outer ear Outer ear The outer ear is the external portion of the ear, which consists of the pinna , concha, and auditory meatus. It gathers sound energy and focuses it on the eardrum .... not equalizing with surrounding pressure	Make sure that your hood does not make an airtight seal over the outside ear hole; never wear earplugs.
Damage to other body air spaces, such as the paranasal sinus Paranasal sinus Paranasal sinuses are air-filled spaces, communicating with the nasal cavity, within the bones of the skull and face.... es.	Obstruction to the sinus ducts	Do not dive with conditions such as the common cold Common cold Acute viral rhinopharyngitis, or acute coryza, usually known as the common cold, is a highly contagious, virus infectious disease of the upper respiratory system, primarily caused by picornaviruses or coronaviruses....
Squeeze damage to blood vessels around the eyes	Caused by suction from the air space inside a mask ("mask squeeze") which is not a fullface mask	Let air into the mask through the nose. Do not dive with eyes-only goggles Goggles Goggles or safety glasses are forms of Eye protection that usually enclose or protect the eye area in order to prevent particulates, water or chemicals from striking the eyes.... .
Squeeze damage to skin under folds in a drysuit	Suction into the space inside the fold	Modern drysuits have a tube connection to inflate the drysuit from the cylinder
Lung squeeze: blood in lungs	Extreme depth when snorkelling	Use an underwater breathing set Breathing set Scuba set, used underwaterRebreather, reprocesses exhaled airSurface supplied diving, fed from the surfaceSelf-contained breathing apparatus, used out of water, worn by rescue workers, firefighters, and others...
Helmet squeeze, with the old standard diving dress Standard diving dress A standard diving dress consists of a metallic diving helmet, an airline or air hose from a surface supplied diving air diving pump, a canvas diving suit, diving knife and boots.... . This does not happen with scuba Scuba set A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving.... where there is no solid pressure-tight helmet	A valve in the helmet failing. In severe cases much of the diver's body could be mangled and compacted inside the helmet	Keep equipment in good order and inspected. Proper training in its use.

On ascent

Air spaces within the body expand when the outside pressure decreases. This can happen from holding the breath on ascent, or from losing control of buoyancy

Buoyancy

In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body....
causing excessive vertical speed during ascent. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
Type	Cause	How to avoid it
Pulmonary barotrauma: "burst lung"	Holding the breath while ascending	Never hold your breath while diving with breathing apparatus
This can cause:
Pneumothorax Pneumothorax In medicine , a pneumothorax, or collapsed lung, is a potential medical emergency caused by accumulation of air or gas in the pleural cavity....	Collapsed lung, air loose in the pleural cavity Pleural cavity In human anatomy, the pleural cavity is the body cavity that surrounds the lungs. The lungs are surrounded by the pleurae, a serous membrane which folds back upon itself to form a two-layered, membrane structure....
Interstitial emphysema Emphysema Emphysema is a chronic obstructive pulmonary disease . It is often caused by exposure to toxin Chemical substance, including long-term exposure to tobacco smoking....	Gas trapped in the chest after burst lung
Subcutaneous emphysema Emphysema Emphysema is a chronic obstructive pulmonary disease . It is often caused by exposure to toxin Chemical substance, including long-term exposure to tobacco smoking....	Gas loose under the skin.
Gas embolism	Air or other gas in the blood stream. Its effects can be very similar to decompression sickness Decompression sickness 'Decompression sickness' , 'the diver?s disease', 'the bends', 'caisson disease' is the name given to a variety of symptoms suffered by a person exposed to a decrease in the pressure around the body.... .
Pain in a sinus Paranasal sinus Paranasal sinuses are air-filled spaces, communicating with the nasal cavity, within the bones of the skull and face....	Blockage of the sinus's duct	Do not dive with nasal congestion, e.g. the common cold Common cold Acute viral rhinopharyngitis, or acute coryza, usually known as the common cold, is a highly contagious, virus infectious disease of the upper respiratory system, primarily caused by picornaviruses or coronaviruses.... .
Eardrum bursting outwards	Blocked Eustachian tube Eustachian tube The Eustachian tube is a tube that links the pharynx to the middle ear. In adults the Eustachian tube is approximately 35 mm long. It is named after the sixteenth century anatomist Bartolomeo Eustachi....

Effects of breathing gas at high pressure

Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
Type	Cause	How to avoid it
Decompression sickness Decompression sickness 'Decompression sickness' , 'the diver?s disease', 'the bends', 'caisson disease' is the name given to a variety of symptoms suffered by a person exposed to a decrease in the pressure around the body.... ("the bends")	Gas dissolves in blood under pressure according to Henry's Law Henry's law In chemistry, Henry's law is one of the gas laws, formulated by William Henry in 1803. It states that:An equivalent way of stating the law is that the solubility of a gas in a liquid is proportional to the pressure of that gas above the liquid.... over time. After dive, ascending too quickly will cause gas to supersaturate and form bubbles in tissue Biological tissue Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function.... s according to time and depth of the dive.	Plan your dive. Know how long you can stay at the planned depth and still make a normal ascent. If stops are necessary, do not miss or cut short decompression stop Decompression stop A decompression stop is a period of time a SCUBA diving must spend at a constant depth in shallow water at the end of a dive to safely eliminate absorbed inert gases from the diver's body to avoid decompression sickness.... s. Training in using diving tables and a dive computer Dive computer A dive computer or decompression meter is a device used by a Scuba diving to measure the time and depth of a dive so that a safe ascent rate can be calculated and displayed so that the diver can avoid decompression sickness.... . See decompression sickness Decompression sickness 'Decompression sickness' , 'the diver?s disease', 'the bends', 'caisson disease' is the name given to a variety of symptoms suffered by a person exposed to a decrease in the pressure around the body.... for a detailed list of the symptoms. Provide something for the diver to hold onto while decompressing.
Bends in snorkellers. Uncommon but known.	Many deep dives in succession. See taravana Taravana Taravana is a disease among Polynesian island natives who habitually free-diving many times in close succession, usually for food or pearls.It seems to be decompression sickness.... .	Use an underwater breathing set Breathing set Scuba set, used underwaterRebreather, reprocesses exhaled airSurface supplied diving, fed from the surfaceSelf-contained breathing apparatus, used out of water, worn by rescue workers, firefighters, and others...
Nitrogen narcosis Nitrogen narcosis Narcosis while diving, commonly called nitrogen narcosis, inert gas narcosis or rapture of the deep, is a reversible alteration in consciousness in Scuba diving at depth....	Breathing a high partial pressure Partial pressure In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.... of nitrogen Nitrogen Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.... (or other inert gas, to varying degrees)	Do not dive too deep on ordinary air. With mixture diving, use the correct breathing gas.
Oxygen toxicity Oxygen toxicity Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen at elevated partial pressures. It is also known as oxygen toxicity syndrome, oxygen intoxication, hyperoxia, or the Paul Bert effect and Lorrain Smith effect, after the researchers who pioneered its discovery and desc...	Breathing a high partial pressure Partial pressure In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.... of oxygen Oxygen Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...	This hazard is well known with rebreather Rebreather A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere.... s. This can happen in very deep diving with open-circuit scuba.
HPNS: High Pressure Nervous Syndrome or Helium Tremors	Breathing a high partial pressure Partial pressure In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.... of helium Helium Helium is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2....	Use another diving technique, such as an ROV Rov Rov is a Talmudic concept which means the majority.It is based on the passage in Exodus 23;2: "after the majority to wrest" , which in Rabbinic interpretation means, that you shall accept things as the majority.... ; or add a little nitrogen as described at HPNS.

The term dysbarism

Dysbarism

Dysbarism refers to medical conditions resulting from changes in ambient pressure. Various activities are associated with pressure changes. Scuba diving is the most frequently cited example, but pressure changes also affect people who work in pressurized environments , and people who move between different altitudes....
describes Decompression sickness

Decompression sickness

'Decompression sickness' , 'the diver?s disease', 'the bends', 'caisson disease' is the name given to a variety of symptoms suffered by a person exposed to a decrease in the pressure around the body....
, arterial gas embolism, and barotrauma

Barotrauma

Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid....
.

Divers face specific physical and health

Health

In 1948, the World Health Organisation defined health as ?a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.? ...
risk

Risk

Underwater

Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river....
(e.g. with scuba) or use high pressure breathing gas

Breathing gas

Caisson (engineering)

Other risks encountered by people in water

Types of this class of diving disorder, and how to avoid them. Click on the boldface links to find symptoms and more information for each topic.
Where it says "Avoid diving with bare skin", a boilersuit could be worn in very warm water.
Type	Cause	How to avoid it
Hypothermia Hypothermia Hypothermia is a condition in which an organism's temperature drops below that required for normal metabolism and bodily functions. In warm-blooded animals, core body temperature is maintained near a constant level through biologic homeostasis....	Losing body heat to the water. Water carries heat away far better than air.	In cool or cold water, wear an adequately warm diving suit Diving suit A diving suit is a garment or device designed to protect a diver from the underwater environment. Modern diving suits can be divided into two kinds:... for the conditions. Also, much heat can be lost from a head without a hood.
Cuts, sometimes with coral tissue left in them	Coral Coral Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....	Do not get too close to coral. Avoid diving with bare skin.
Cuts	Rock, metal, etc	Avoid diving in bare skin, particularly in caves or shipwrecks.
Stings	Fire coral Fire coral Fire corals are colonial marine organisms that look rather like real coral. However they are technically not corals; they are actually more closely related to jellyfish and other stinging Sea anemone....	It is yellow. Learn to identify it.
Stings, some dangerous	Some jellyfish Jellyfish Jellyfish are free-swimming members of the phylum Cnidaria. They have several different morphologies that represent several different cnidarian classes including the Scyphozoa , Staurozoa , Cubozoa , and Hydrozoa ....	Learn about the dangerous species. Avoid diving with bare skin.
A deep cut which leaves poison in the wound	sting ray (its self-defence reaction)	Do not poke about in sand where they live. Care when wading.
Reef rash	A generic catch-all term that refers to the various cuts, scrapes, bruises and skin conditions that result from diving in tropical waters. This includes sunburn, jellyfish stings, sea lice bites, fire coral inflammation and other skin injuries that a diver may gain from using a shorty wetsuit or no diving suit.	Wear a full-body exposure suit to prevent direct skin to environment contact.
Poison-injecting spines	lionfish Lionfish A Lionfish is any of several species of venomous marine fish in the genus Pterois, Parapterois, Brachypterois, Ebosia or Dendrochirus, of the family Scorpaenidae.... , stonefish Stonefish *Synanceja verrucosa* is a fish species, sometimes lethal to humans, which is known as the reef stonefish or simply stonefish. They are carnivorous Actinopterygii with venom spines that lives on reef bottoms, camouflaged as a rock.... , crown of thorns starfish, some sea urchin Sea urchin Sea urchins are small, spiny, globular creatures that compose most of class Echinoidea. They are found in oceans all over the world. Their shell, or "test", is round and spiny, typically from 3 to 10 cm across.... s in warm seas	Learn to identify them. Keep away from them. Care when wading.
Poison injection	Blue ringed octopus, in parts of the Pacific Ocean Pacific Ocean The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portugal explorer Ferdinand Magellan....
Shark Shark Sharks are a type of fish with a full Cartilage skeleton and a highly Streamlines, streaklines and pathlinesd body. They respire with the use of five to seven gill slits.... bites	Sharks, likelihood of risk is location dependent	Consult location-specific information to determine risk; never molest even seemingly-tame sharks underwater.
Crocodile Crocodile A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e.... attack	Crocodiles, in some tropical waters	Get proper information on them
Attack by an unusually large grouper Grouper For other meanings, see Grouper .Groupers are fish of any of a number of genus in the subfamily Epinephelinae of the family Serranidae, in the order Perciformes.... .	Epinephelus lanceolatus can grow very big in tropical waters, where protected from attack by shark Shark Sharks are a type of fish with a full Cartilage skeleton and a highly Streamlines, streaklines and pathlinesd body. They respire with the use of five to seven gill slits.... s.	Get proper information on them. A throat inlet that can expand to 2 feet square can swallow a scuba diver.
Electrocution Electric shock An electric shock can occur upon contact of a human's body with any source of voltage high enough to cause sufficient Electric current through the muscles or hair....	Electric eel Electric eel The electric eel, temblador Electrophorus electricus, is an electrical fish. It is capable of generating powerful electricity shocks, which it uses for both hunting and self-defense.... , in some South America South America South America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere.... n fresh water	Get proper information on them
	Electric ray Electric ray The electric rays are a group of batoid, flattened cartilaginous fish with enlarged pectoral fins, that comprise the order Torpediniformes.... , in some warm seas	Get proper information on them
	It is said that some naval anti-frogman Frogman A frogman is someone who is trained to dive or swim in a military capacity which can include combat. Such personnel are also known by the more formal names of combat diver or combat swimmer.... defences use electric shock	Keep out of armed forces areas
Powerful ultrasound Ultrasound Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing . Although this limit varies from person to person, it is approximately 20 Hertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound....	It is said that some naval anti-frogman Frogman A frogman is someone who is trained to dive or swim in a military capacity which can include combat. Such personnel are also known by the more formal names of combat diver or combat swimmer.... defences use powerful ultrasound. Also used for long-range communication with submarines	Keep out of armed forces areas. Avoid large ships' ordinary sonar Sonar Sonar is a technique that uses sound propagation to navigation, communicate with or detect other vessels. There are two kinds of sonar: active and passive.... . See Underwater Port Security System Underwater Port Security System The Coast Guard unveiled the system on 2 or 9 February 2005 at the Coast Guard Integrated Support Command in San Pedro, California, USA.... .
Exposure to disease carried by in-water organisms	Weil's disease Leptospirosis Leptospirosis is a infectious disease zoonotic disease caused by spirochaetes of the genus Leptospira that affects humans and a wide range of animals, including mammals, birds, amphibians, and reptiles.... (in rat's urine) Bilharzia (in some warm fresh water) Various bacteria Bacteria The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals.... found in sewage Sewage Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of washing water, feces, urine, laundry waste and other material which goes down Plumbing fixture from households and industry....	In affected water, dive in watertight drysuit and full face diving mask 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 or demand valve that provides the diver with breathing gas....
Exposure to harmful chemicals in the water	May be found in water polluted by industrial waste outfalls or by natural sources. For example hydrogen sulfide Hydrogen sulfide Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence.... in some lakes and caves can be absorbed through the skin.
Broken bone Bone Bones are rigid organ that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red blood cell and white blood cells and store minerals.... s, bleeding Bleeding Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood from the circulatory system. Bleeding can occur internally, where blood leaks from blood vessels inside the body or externally, either through a natural opening such as the vagina, Mouth , nose, or anus, or through a break in the skin.... wound Wound In medicine, a wound is a type of injury in which the skin is torn, cut or punctured , or where blunt force physical trauma causes a bruise . In pathology, it specifically refers to a sharp injury which damages the dermis of the skin.... s and other trauma Physical trauma Physical trauma refers to a body injury. A trauma patient is someone who has suffered serious and life-threatening physical injury with the potential for secondary complications such as Shock , respiratory failure and death....	Colliding with a boat Boat A boat is a watercraft of modest size designed to float or plane on water, and provide transport over it. Usually this water will be inland or in protected coastal areas.... or its propellor. Wave Wave A wave is a disturbance that propagates through space and time, usually with transference of energy. While a mechanical wave exists in a medium , waves of electromagnetic radiation can travel through vacuum, that is, without a medium.... action on the shore.	Use Surface detection aids Diving equipment The fundamental item of diving equipment used by divers is the Scuba sets, such as the Aqua-Lung or Rebreather. There are other important pieces of equipment that make diving safer, more convenient or more efficient.... or a diving shot Diving shot A diving shot is an item of diving equipment consisting of a weight, a line and a buoy.... to mark surfacing position and aid searchers. Plan a safe exit point and check weather Weather Weather is a set of all the Phenomenon occurring in a given atmosphere at a given time. Weather phenomena lie in the hydrosphere and troposphere.... and tidal conditions.
Diver lost at sea after a boat dive	Separated from boat cover due to poor visibility at surface or strong underwater currents.
Diver lost at sea after a shore dive	Big waves made it unsafe to leave the water; currents moved the diver away from a safe exit; surface weather on the shore make the sea too rough to safely exit.
Sudden loss of underwater visibility	Silt out Silt out A silt out is a situation when underwater visibility is rapidly reduced to zero.It often happens from divers' swimfins disturbing silt, particularly in caves or in still fresh water.... : stirring up silt or other light loose material	Training in diving in zero visibility. Learn the frog kick Frog kick The frog kick is a swimming action sometimes used by scuba divers when they are swimming near a soft silty seabed or lakebed which they do not want to stir up damaging the visibility.... .

Diving hazards and precautions

The ordinary features of diving

Effects of relying on breathing equipment while underwater

Effects of barotrauma or pressure damage

On descent

On ascent

Effects of breathing gas at high pressure

Other risks encountered by people in water

See also

External links