List of Diving Hazards and Precautions

7/30/2019 List of Diving Hazards and Precautions

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List of diving hazards and precautions

The aquatic environment

Hazard Consequences Cause Avoidance and prevention

Any liquid

environment.

Asphyxia bydrowning.

Inhalation of liquid (water), usually causinglaryngospasm

and suffocation caused by water entering the lungs andpreventing the absorption of oxygen leading to cerebral

hypoxia.[3]

Avoid out of air emergencies underwater. Provide appropriate buoyancy. Avoid or prevent accidents resulting in

unconsciousness.

Use of a full face mask. Use of helmet. Use of surface supplied diving equipment with voic

communications.

Adequate swimming skills and fitness for thecircumstances.

Use of snorkel when appropriate. Lifejackets which hold the wearer's face above the

water may be worn when appropriate.

[edit] Use of breathing equipment in an underwater environment


Oxygenpartial

pressurein the

breathing gas is

too low to

sustain normalactivity or

consciousness.

Hypoxia:

Reducedlevel of consciousness,seizures,coma, death. Severe

hypoxia induces a blue

discoloration of the skin, calledcyanosis, but this may also be

present in a diver due toperipheral vasoconstriction

resulting from exposure to cold.

Equipment failure: A faulty or misusedrebreather

can provide the diver with hypoxic gas. Correct maintenance, preparation and pre-use

procedures and checks.

Correct use of recommended procedures andchecklists when preparing for use.

Adequate and redundant instrumentation formonitoring gas quality during use.

Constant vigilance during use.
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There is typically no warning of

onset or development. Theextreme case, anoxia, implies an

absence of oxygen and is rapidlyfatal.

Adequate bailout facilities in case of failure. Adequate training in the use of rebreathers in general

and the specific model.

Somebreathing gasmixtures for deep diving such

astrimixandhelioxare hypoxic at shallow depths,

and do not contain enough oxygen to maintain

consciousness, or sometimes life, at or near thesurface.

[5]

Gas requirements planned to suit the intended diveprofile.

Use of a travel mix for descent and a decompressionmix for ascent through the depth range where thebottom gas is hypoxic.

Safe procedures used for gas changes.[6] Gas switches planned and executed at

appropriate depths.[5]

Depth and ascent rate accurately monitoredand controlled.

Clear and unambiguous identification ofcylinder gases.

Adequate training in the use of mixed gases.

Internal corrosion of full cylinder standing for along time can potentially use up some of the

oxygen in the contained gas before the diver usesthe cylinder.[citation needed]

Routine periodical inspection and testing ofcylinders.

Analysis of oxygen fraction of gas before use,particularly if cylinder has been stored for a long

time.

Loss ofbreathing gas

supply.

May result indrowning,

occasionallyasphyxiawithout

water aspiration.

Equipment failure: Several modes are possible.

Closing and jamming of the cylinder valveby rolloff

[7]on an overhead.

[8]

Rupture of a bursting disc[9]overpressureprotection on a cylinder valve.

Rupture of a regulator hose or loss of theend component, leaving an open hose end.

Unrecoverable free flow[10]of a second

Appropriate maintenance and servicing ofequipment.

Inspection of the external condition, and testing ofthe function of equipment before use.

Use only of equipment in good working condition. Connection and mounting of equipment to minimise

risk of damage.

Avoidance of damage to equipment during dives. Use of two fully independent breathing gas
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stage.

Freezing of a first stage regulator, lockingthe valve mechanism open, and consequent

free flow of the demand valve due toexcessive interstage pressure.

O-ring failure at the connection of aregulator to a cylinder valve.

supplies.[11

Use ofbailout gas supply.

Thebuddy system, when correctly followed, allows

the diver's buddy to supply breathing gas in anemergency.

"H" or "Y" type cylinder valvesor manifolded twin

cylinders with two cylinder valves allow the

dysfunctional supply to be closed to prevent total

loss, and the other regulator to be used for theremaining gas supply.

Dual independent cylinders ensure that if onecylinder supply fails there is another available.

Use ofDIN connectionscan reduce the risk ofcatastrophic O-ring failure.[12]

Emergency free ascentmay be possible, and is

generally more survivable than drowning.

Running out of breathing gas because of poor gasmonitoring discipline[13]

Adequate training of divers. Disciplined attitude and situational awareness during

dives. Use ofreserve valve. Use ofsurface supplied diving equipment.

Use of bailout gas supply. The buddy system, when correctly followed, allows

the diver's buddy to supply breathing gas in anemergency.

Running out of breathing gas because of being

trapped bynetsor lines Situational awareness underwater. Use of adiver's net cutter, ordive tool/knifeto cut

free of entanglement.

Carrying sufficient gas in reserve to allow areasonable amount of time to deal with emergencies.

Running out of breathing gas because of beingtrapped or lost in enclosed spaces underwater, such

Appropriate safety equipment and procedures toavoid getting lost (cave lines).
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ascavesorshipwrecks.

Specific training for overhead diving. Seecavedivingandwreck diving.

Assess stability of underwater structures and avoidentry if a structure is unstable.

Inhalation of

salt spray

Salt water aspiration syndrome: a

reaction to salt in thelungs. Early

symptoms are:

[14]

Post-dive cough, with orwithout sputum, usually

suppressed during thedive.

In serious cases thesputum may be

bloodstained, frothy andcopious.

Over time furthersymptoms may develop,

including:

rigors, tremors orshivering;

anorexia, nauseaor vomiting;

hot or coldsensations;

dyspnoea; cough;sputum;

headaches;malaise; and

generalised aches.

Inhaling a mist ofsea waterfrom a faultydemand

valve Appropriate maintenance and servicing of

equipment.

Inspect external condition and test function beforeuse.(specifically test the seal of exhaust valves andpossible leaks in the second stage casing and

mouthpiece before opening the cylinder valve).

Use equipment only if it is in good workingcondition.

Use ofalternative air sourceif DV breathes wetduring dive.

The technique of inhaling slowly and using thetongue to deflect spray particles may be effective as

a temporary mitigation.

Carbonmonoxide

contamination

Carbon monoxide poisoning.

Contaminated air supplied by a compressor whichsucked in products ofcombustion, often its own

engine'sexhaust gas. Aggravated by increased

Adequate precautions to ensure that intake is inuncontaminated air when operating breathing air

compressors.
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of breathing gas

Initial symptoms include:headache,nausea,

malaise, andfatigue.[15]

Headache is themost commonsymptom; it is

often described asdull, frontal, and

continuous.[16]

Increasing exposureproduces cardiac

abnormalities includingfast heart rate,low blood

pressure, andcardiacarrhythmia;[17][18]central

nervous systemsymptomsincludedelirium,

hallucinations,dizziness,unsteady gait,confusion,

seizures,central nervoussystem depression,

unconsciousness,respiratory arrest, and

death.[19][20]

partial pressure due to depth. Periodical air quality testing of compressors. Use of compressor output filter containing

"Hopcalite" catalyst to convert possible carbon

monoxide contamination to less hazardous carbondioxide.

Test air quality before use (portable carbonmonoxide analysers are available and may be worth

using in places where air quality is questionable)

Air contaminated with carbon monoxide is oftencontaminated by substances which have a smell ortaste. Air which smells or tastes of exhaust fumes

should not be breathed.

Oil getting into the air and partially oxidising in thecompressor cylinder, like in adiesel engine[citationneeded]

, due to worn seals and use of unsuitable oils,or an overheated compressor.

Adequate maintenance of the compressor. Use of correct oil rated for breathing air compressor

lubrication.

Ensure compressor running temperature is withinmanufacturer's specifications.

Ensure adequate supply of cooling air to compressor. Compressor should not be run when ambienttemperatures exceed manufacturer's limits.

Hydrocarbon(oil)

contamination

of air supply.

Emphysemaorlipid pneumonia(more to be added)

Caused by inhaling oil mist. This may happengradually over a long time and is a particular risk

with a surface supplied air feed.

Use of a suitable separators and airfilteraftercompression.

Monitor and drain separators and changefilters as necessary.

Periodic testing of delivered air quality.
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edia.org/wiki/Hypotensionhttp://en.wikipedia.org/wiki/Hypotensionhttp://en.wikipedia.org/wiki/Tachycardiahttp://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-16http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-JToxClinTox1994-hardy-15http://en.wikipedia.org/wiki/Fatigue_(medical)http://en.wikipedia.org/wiki/Malaisehttp://en.wikipedia.org/wiki/Nauseahttp://en.wikipedia.org/wiki/Headache


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Smell and taste can distinguish oilcontamination in many cases.

Passing a metered quantity of the air throughan absorbent filter paper may show up an oildeposit

Directing air flow onto a clean mirror surfaceor glass sheet may show gross contamination

Excessivecarbon dioxide

in breathing gas

Carbon dioxide poisoningorhypercapnia.[21][22]

Symptoms and signs ofearly hypercapnia

include: flushed skin, fullpulse,increased breathing

rate,shortness of breath,muscle twitches, hand

flaps, reduced neuralactivity, headache,

confusion, lethargy,increased cardiac output,

an elevation in arterialblood pressure, and a

tendency forcardiacarrhythmias.[23][24]

In severe hypercapnia(generally partial pressure

of CO2 greater than 10kPa), symptoms progress

todisorientation,panic,hyperventilation,

convulsions,unconsciousness, and

eventually death.[25][26]

Re-inhalingcarbon dioxide-laden exhaledgas due to excessivedead spacein

breathing apparatus.

Shallow breathing - not exchangingsufficient air during a breathing cycle.

Minimise the volume of any enclosed spaces whichthe diver breathes through. For example, this can

happen with diving with a large "bubblehead"

helmet.

Avoiding breathing shallow (low volume) breaths.

Thescrubberof a divingrebreather, fails to absorbenough of the carbon dioxide in recirculated

breathing gas. This can be due to the scrubberabsorbent being exhausted, the scrubber being too

small, or the absorbent being badly packed orloose, causing "tunneling" and "scrubberbreakthrough" when the gas emerging from the

scrubber contains excessive carbon dioxide.

Adequate maintenance of rebreathers. Correct packing and assembly of scrubber canisters. Pre-use inspection and testing of rebreathers using

an appropriate checklist.

Use of correct scrubber absorbent material. Use of absorbent that is of good working quality. Discard absorbent after use. Use of carbon dioxide monitoring instruments. Adequate training in the recognition of hypercapnia

before using a rebreather.

Bail-out to open circuit if carbon dioxide levels gettoo high.

Filling of cylinders with compressed air taken froman area of raised concentration of carbon dioxide.

Siting the compressor air intake in an area of freshair and ducting it to the compressor.

Passing intake air through a carbon dioxide scrubberelement before compression.

Periodical air quality testing of compressors.

Breathing the Consequences depend on the The wrong gas was put in a cylinder. Cylinders should be filled by competent people.
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wrong gas circumstances, but may include

oxygen toxicity, hypoxia,nitrogen narcosis, anoxia, and

toxic effects of gases notintended for breathing. Death or

serious injury is likely.

A cylinder was marked or labelledincorrectly.

A correctly labelled cylinder was mistakenby the user.

The diver unintentionally switches to thewrong gas during a dive.

Clear instructions, preferably written, for thecomposition of the gas to be mixed will reduce therisk of filling with the wrong gas.

Clear, unambiguous and legible labels indicatingmaximum operating depth and cylinder contents,

applied in a way that the user will be able topositively identify the gas at the time when it is to be

used can prevent confusion and inadvertent use of

the wrong gas. Analysing gas after filling, before accepting

delivery, and before use (before the dive) may detect

errors in labelling or composition in time to take

corrective action.

Procedures designed to positively identify the gasmay be used when switching mixes.

Valves which change gas mixes may be fitted with apositive interlock preventing accidental orinadvertent switching, and may include a method of

confirming the gas connected by feel.

Displacement of

demand valve(DV) from the

diver's mouth.

Inability to breathe until demand

valve is replaced. This should notnormally be a major problem as

techniques for DV recovery are

part of basic training.Nevertheless it is an urgent

problem and may be exacerbatedby loss of the mask and/or

disorientation.

Unconscious diver releases grip onmouthpiece.

DV is forcibly knocked or pulled from thediver's mouth by impact with surroundings

or another diver.

Use of full face mask reduces risk of loss of DV as itis strapped to the head and can not be dropped if thediver loses consciousness.

Adequate training and practice of DV recoveryskills.

Use of an alternative air source such as octopus DVor bailout cylinder which can be used if the primaryDV is not immediately accessible.

Mounting the alternative air source and DV so that itis easily accessible in an emergency and protected

from damage when not in use.

[edit] Exposure to a pressurised environment and pressure changes

See also:barotraumaandpressure
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[edit] Pressure changes during descent

-


Sudden chilling of the

inner ear.

Vertigo, includingdizzinessand

disorientation, particularly if one side ismore chilled than the other.

Cold water in theouter earpassage,

chilling the innerear, particularly severe ifthe eardrum is ruptured.

Use of a hood to keep the head covered. Water leaking i

the hood will warm up before entering the external audiopening and will be reasonably warm before reaching th

eardrum, and will soon reach body temperature if flushiminimised

Pressure difference over

eardrum

Burst or stretched eardrum:

The eardrum is stretched due to a pressure

difference between the outer and middleear spaces. If the eardrum stretches

sufficiently, it may rupture, which is morepainful. Water entering the middle ear

may cause vertigo when the inner ear iscooled. Contaminants in the water may

cause infection.[27]

The pressure in themiddle earnot

equalizing with external (ambient)

pressure, usually due to failure to clear theEustachian tube.[27]

Ears can beequalizedearly and often during the descent

before the stretching is painful.

The diver can check if the ears will clear on the surface precondition for diving[27]

Reversed ear may be caused by the outer

ear passage being blocked and thepressure remaining low, while the middle

ear pressure increases by equalising with

ambient pressure through the eustachiantubes, casing a pressure differential andstretching the eardrum, which may

eventually rupture.[28]

The hood should not make an airtight seal over toutside ear opening.

Sealed earplugs should never be worn whilediving.

[28]

Pressure differencebetweenparanasal sinus

and ambient pressure.

Sinus squeeze:Damage to the sinuses usually resulting in

pain, and often burst blood vessels andnosebleed.[29]

Obstruction to the sinus ducts leading topressure differences between the interior

of the sinus and the external pressure.[29]

Do not dive with conditions such as thecommon coldoallergies which cause nasal congestion[29]

Localised low pressure

in the diving mask.

Mask squeeze:

Squeeze damage to blood vessels aroundthe eyes[30]

Caused by local low pressure in the air

space inside a diving half-mask. Ambientpressure increase during descent not

balanced inside mask air space.

Mask squeeze can be avoided by allowing air intthe mask through the nose whenever the pressurdifference is noticeable.

Afullface maskwill automatically equalise throthe demand valve.

Air filled eyes-onlygogglescan not be equalisedare not suitable for diving.
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ikipedia.org/w/index.php?title=List_of_diving_hazards_and_precautions&action=edit&section=4


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Reduction of volume of

airspace indrysuit. Loss of buoyancy. Suit squeeze injury (usually

restricted to bruising and minor

abrasion) to skin.[30]

Volume of air in a drysuit reducesas pressure increases with depth.

Skin may be pinched by folds in adrysuit as the air inside iscompressed.

Modern drysuits have a low pressure air hose connectio

and valve to inflate the drysuit from the cylinder. Addinsufficient air to maintain the bulk of the undersuit will

prevent suit squeeze and stabilize buoyancy of the suit.

Pressure differencebetween lung gas

contents and ambientpressure

Lung squeeze: Lung damage Free diving to extreme depth. It can be avoided by limiting free diving depth to capacof lungs to compensate,[31]and by training exercises to

increase compliance of chest cavity.[citation needed]

Rupture or supply pressure failure of asurface supply hose with simultaneous

failure of the non-return valve.[31]

Maintenance and pre-dive tests of non-return valves on helmet or full face mask.

Helmet squeeze, withthe oldstandard diving

dress. (This can nothappen withscubaor

where there is no rigid

pressure-tight helmet)

In severe cases much of the diver's bodycould be mangled and compacted inside

the helmet, however, this requiressubstantial pressure difference, or by a

sudden considerable increase in depth, as

when the diver falls off a cliff or wreck

and descends faster than the air supply cankeep up with the pressure increase.

A non-return valve in the air supply line tothe helmet failing (or absent on the

earliest models of this type of diving suit),accompanied by a failure of the air

compressor (on the surface) to pump

enough air into the suit for the gas

pressure inside the suit to remain equal tothe outside pressure of the water, or aburst air supply hose.

Appropriate maintenance and daily pre-use testing of noreturn valves

A sudden large increase in ambient

pressure due to sudden depth increase,when the air supply can not compensate

fast enough to prevent compression of theair in the suit.

The squeeze due to depth changes was more likewhen the air supply was powered by men. Motocompressors are usually able to supply air much

faster, so an adequate air reservoir on thecompressor should prevent this problem.

The diver may be prevented from sinking too deby minimizing slack in the lifeline or umbilical.

The diver may work at neutral buoyancy when this a risk of falling off a structure, or may clip on the structure, but this presents a hazard of

entrapment.

Tooth squeeze[32]

Toothache, most often affects divers with Any gas space inside a tooth due to decay Tooth squeeze may be avoided by ensuring good dental
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10/31

preexistingpathologyin theoral cavity[ or poor quality fillings or caps may allow

tissue inside the tooth to be squeezed intothe gap causing pain.

hygiene and that all fillings and caps are free of air spac

Suit compression. Loss of buoyancy may lead to:

Uncontrolled descent. Inability to achieve neutral

buoyancy.

Inability to surface due toinsufficient buoyancy

Difficulty in controlling depth andascent rate. This can be criticalwhen decompression is required,

and oxygen rich breathing gasesare used.

Buouyancy loss due to compression of

foam neoprene wet or drysuit material. Use of buoyancy compensator with volume

appropriate to expected buoyancy variation durindive.

Use of appropriate ballast weight for dive profileequipment in use.

Use of inflation system for replacing lost volumdrysuits.

Excessive weighting makes buoyancy control mdifficult and loss of control more likely.

Adequate training and practice of buoyancy contskills.

[edit] Pressure changes during ascent


Lung overpressure:Pressure in lungs

exceeds ambientpressure.

Pulmonary barotrauma(Lungoverexpansion injury) - rupture of lung

tissue allowing air to enter tissues, bloodvessels, or spaces between or surrounding

organs:

Pneumothorax: Free air in thepleural cavity, leading to collapsed

lung.

Interstitialemphysema: Gastrapped in the spaces betweentissues.

Mediastinal emphysema:Gas trapped around the

Failing to maintain an open airway torelease expanding air while ascending.

Divers should not hold their breath while ascending aftediving with breathing apparatus:

The best option is to breathe normally whileascending when possible, and exhale duringfree

ascent.[34]

Forced exhalation before starting an emergency ascent may increase risk of lung overpressure

injury.[34]
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heart.

Subcutaneousemphysema: Freegas under the skin.

ArterialGas embolism: Air orother breathing gas in the bloodstream, causing blockage of small

blood vessels.

Sinusoverpressure. Sinus overpressure injury is commonlyrestricted to rupture of mucous membrane

and small blood vessels, but can be moreserious and involve bone damage.[citation

needed]

Blockage of the sinus's duct, preventingtrapped air in a sinus from equalising with

the pharanx.

Not diving with nasal congestion, e.g. Hay feverthecommon cold.

Checking pefore a dive to ensure that sinuses anmiddle ears will equalise without undue effort.

Systemicdecongestantshave been used successfbut may have undesirable side-effects, and there

risk that they will wear off before surfacing. Topdecongestants do not usually have sufficient last

effect.

Middle ear overpressure Injury (reversed ear) of eardrum stretchingor bursting outwards due to expansion of

air in the middle ear

BlockedEustachian tubefails to allowpressure to equalise middle ear with the

upper airway.

Overpressure within acavity in a tooth, usuallyunder a filling or cap.

Tooth squeeze/Toothache, may affectdivers with preexistingpathologyin theoral cavity.

Tooth pain, loss of fillings,cracking of teeth.

Gas may find its way unto a cavity in thetooth or under a filling or cap during adive and become trapped. During ascent,

this gas will exert pressure inside thetooth.

Good dental hygiene, and maintenance of dental repairsprevent or remove potential gas traps.

Suit and BC expansion Loss of buoyancy control - uncontrolledascent.

Expansion of neoprene suit material, gascontent of dry suits and buoyancy

compensators increasing buoyancy of the

diver.

Automatic dump valves in dry suits. Monitoring of buoyancy on a continuous basis w

in mid-water, and manually adjusting volume of

buoyancy compensator when necessary.

Appropriate training and practice to develop goobuoyancy control skills to suit the equipment in

Ability to recover from inversion in dry suit. Maintaining the minimum air volume for adequa

liner bulk maintenance in a dry suit, as this preve
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excessive buoyancy shifts. This implies use of B

for buoyancy control, not the suit.

Minimizing weighting to what is actually necessso compensatory air volume is minimized. Thisreduces the magnitude and rate of buoyancy cha

with pressure change.

[edit] Breathing gases at high ambient pressure


Medium to long term

exposure to high partialpressures (>c1.3 bar) of

inert gas (usually N2 orHe) in the breathing gas.

Decompression sickness("the bends"):

Injury due to gas bubbles expanding in thetissues and causing damage, or gas

bubbles in the arterial circulation causingemboli and cutting off blood supply to

tissues downstream of the blockage.

Gas dissolved in tissues under pressure

during the dive according toHenry's Lawcoming out of solution and forming

bubbles if the ascent anddecompressionistoo fast to allow safe elimination of the

gas by diffusion into the capillaries and

transport to the lungs where it can diffuseinto the respiratory gas.

Although rare, decompression sickness ispossible in free-diving (breathhold diving)

when many deep dives are done insuccession. (See alsotaravana).

Decompress to suit the dive profile and gas mixtused.

Use appropriate ascent rates and decompressionstops.

Oxygen-rich gas mixtures may be used to acceledecompression.

Use depth control aids to maintain correctdecompression depth.

Avoid dehydration and hypothermia. Maintain cardiovascular fitness.

Short term (immediate

onset) exposure to highpartial pressure (>c2.4

bar) of nitrogen in thebreathing gas:

Nitrogen narcosis:

A reversible alteration inconsciousnessthat occurs whiledivingat depth.

A state similar toalcoholintoxicationornitrous oxide

inhalation. The most dangerous aspects of

narcosis are the loss of decision-

making ability and focus, andimpaired judgement, multi-tasking

A highpartial pressureofnitrogenin the

nerve tissues. (other gases may also havenarcotic effect, to varying degrees).

Related to the increased solubilityof gases in body tissues at elevated

pressure.[35]

Inert gases dissolving in thelipidbilayerofcell membranesmaycause narcosis.[36]

Other possibilities includeneurotransmitter receptorprotein

Use of less narcotic gases to dilute the breathingor

Limit the partial pressure of narcotic gases atmaximum depth by limiting the depth of the div
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and coordination.

Other effects include vertigo, andvisual or auditory disturbances,

exhilaration, giddiness, extremeanxiety, depression, or paranoia,

depending on the individual diver.

mechanisms.[

Short term (minutes to

hours) exposure to highpartial pressure (>c1.6

bar) of oxygen in the

breathing gas.

Acuteoxygen toxicity:

Convulsionssimilar to epilepticseizure. Loss of consciousness

may occur with no warning, ormay be preceded by any of the

following symptoms:

Muscle twitching, Tinnitus, Blurred ortunnel vision, Disorientation, Aphasia, Nystagmus, Incoordination

Breathing gas with too high apartial

pressureofoxygen, risk becomessignificant at partial pressures exceeding

1.6 bar (partial pressure depends upon

proportion of oxygen in the breathing gas,and depth)

Appropriate training before using arebreatheroroxygenenriched gases such asnitrox.

Correct labeling of cylinders containing mixedbreathing gases, specifying oxygen fraction and

maximum operating depth.

Accurate monitoring of dive depth to ensure thatgases are not used below the appropriate maximuoperating depth for the mixture.

Long term (hours to

days) exposure tomoderately raised partial

pressure (>0.5 bar) ofoxygen in the breathing

gas.

Chronicoxygen toxicity:

Signs of pulmonary toxicity beginwith inflammation of the upper

airways.

Temporarily reduced lungcapacity.

Acute respiratory distresssyndrome.

Breathing gas at too high apartial pressure

ofoxygen, Risk is significant at a partialpressure in excess of 0.5 atmospheres

pressure for long periods and increaseswith higher partial pressure even for

shorter exposures.

Not normally a risk for recreational divers due toshort exposures.

Limit use of rich nitrox mixtures and pure oxygefor accelerated decompression.

Limit exposure by calculating Oxygen ToxicityUnits for pre-existing and planned exposures and

keeping below recommended limits.

Most likely to be encountered in recompressiontreatment for decompression illness.

Exposure to a highpartial pressure(>15 bar)

High Pressure Nervous Syndrome(HPNS):

HPNS has two components: The susceptibility of divers to HPNS varies overwide range depending on the individual, but has
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ofheliumin the

breathing gas. Symptomsinclude:[38]

[39]

visualdisturbance nausea dizziness decreasedmentalperformance tremors myoclonic jerking somnolence EEGchanges

The compression effects mayoccur when descending below 500

feet (150 m) at rates greater than afew metres per minute, but reduce

within a few hours once thepressure has stabilised.

The effects from depth becomesignificant at depths exceeding1,000 feet (300 m) and remain

regardless of the time spent at thatdepth.[39]

variation between different dives by the same

diver.[39]

Use another diving technique, such as anatmospheric diving suit,submersibleorROV.

Including other gases in the mix, such asnitroge(creatingtrimix) orhydrogento make (hydrelioxsuppresses the neurological effects.[40][41][42]

[edit] The specific diving environment


Exposure to cold water

during a dive, and coldenvironment before orafter a dive, wind chill.

Hypothermia: Reduced core temperature,

shivering, loss of strength, reduced levelof conscuousness, loss of consciousnessand eventually death.

Loss of body heat to the water or other

surroundings. Water carries heat away farmore effectively than air. Evaporativecooling on the surface is also an effective

mechanism of heat loss, and can affectdivers in wet diving suits while travelling

on boats.

Diving suitsare available which are suited to a wrange of water temperature down to freezing.

[43]

appropriate level of insulation for the conditionsreduce heat loss.

In extreme conditions and when helium basedmixtures are in use as breathing gas, heated suits

may be necessary[citation needed].

On the surface, wind chill can be avoided by stayout of the wind, staying dry, and suitable protectclothing.

Some parts of the body, particularly the head,[43]more prone to heat loss and insulation of these ais correspondingly important.

Nonfreezing Cold Injuries(NFCI). Exposure of the extremities in water

temperatures below 12C (53.6F)

Hand and Foot Temperature Limits to avoid NFCI:[

Fully Functional 18C (64.4F) Non Freezing Co
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Injury Threshold < Week.

12C (54F) approximately 3 hours. 8C (46.4F) for maximum of 30 min. 6C (42.8F) immediate rewarming required.

Protection in order of effectiveness:

Dry gloves attached to drysuit without wrist seal

Dry gloves with wrist seal. Wet suit (neoprene) gloves. Rubberised cloth or leather gloves.

Muscularcramps Inadequate insulation Reduced perfusion to the legs and

feet (occasionally hands)

Better insulation and/or suit fit

Hardcorals Coral cuts - Infected lacerations of theskin.

Sharp coral skeleton edges lacerating orabrading exposed skin, contaminating the

wound with coral tissue and pathogenic

microorganisms.

Coral cuts may be prevented by avoiding contacunprotected skin with coral.

Protective clothing such as wet-suit, dry suit,skin/lycra suit or overalls are effective.

Sharp edges of rock,metal, etc.

Lacerations and abrasions of the skin,possibly deeper wounds.

Contact with sharp edges. Most cuts may be avoided by wearing protectiveclothing such as wet-suit, dry suit, skin/lycra suioveralls.

Avoiding high risk areas such as shipwrecks durstrong water movements such as surge or curren

also effective.

Strength and skill in avoiding contact with sharpedges will help, but does not eliminate the risk w

water movement is strong.

Stinginghydroids. Stinging skin rash, local swelling and

inflammation

Contact of bare skin withfire coral Avoid contact with benthic organisms. Protective clothing such as exposure suits, lycra
http://en.wikipedia.org/wiki/Crampshttp://en.wikipedia.org/wiki/Crampshttp://en.wikipedia.org/wiki/Crampshttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Hydroidshttp://en.wikipedia.org/wiki/Hydroidshttp://en.wikipedia.org/wiki/Hydroidshttp://en.wikipedia.org/wiki/Fire_coralhttp://en.wikipedia.org/wiki/Fire_coralhttp://en.wikipedia.org/wiki/Fire_coralhttp://en.wikipedia.org/wiki/Fire_coralhttp://en.wikipedia.org/wiki/Hydroidshttp://en.wikipedia.org/wiki/Coralhttp://en.wikipedia.org/wiki/Cramps


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skins, or overalls are effective.

Stingingjellyfish Stinging skin rash, local swelling andinflammation, sometimes extremely

painful, occasionally dangerous or evenfatal

Some species of jellyfish (free swimmingcnidaria) have stinging cells which are

toxic to humans, and will inject venom oncontact with the skin.

Avoid contact with jellyfish tentacles. Protective clothing such as exposure suits, lycra

skins, or overalls is effective.

Stingrays A deep puncture or laceration which

leaves venom in the wound

Defensive reaction of asting raywhen

disturbed or threatened, by lashing outwith the venomous spine on the tail.

Stingrays can usually be avoided by not pokingabout on the bottom where they may be hiding,partly or completely buried under a thin layer of

sand.

The risk is usually greater when wading, when thwader may inadvertently step on a buried ray.

Rays are usually very shy and will usually swimaway when approached Risk of injury may be

avoided by not molesting or threatening the animwhen seen, and by staying a safe distance from t

tail

Tropical reefenvironment

Reef rash: General or localised stinging orinflammation of the skin. may include

allergic reactions.

A generic catch-all term that refers to thevarious cuts, scrapes, bruises and skin

conditions that result from diving intropical waters. This may include sunburn,

mild jellyfish stings, sea lice bites, fire

coral inflammation and other skin injuriesthat a diver may get on exposed skin.

A full-body exposure suit can prevent direct skin toenvironment contact.

Fish and invertebrates

with venomous spines.

Puncture wounds with venom injection.

Often extremely painful and may be fatalin rare cases.

Lionfish,stonefish,crown of thorns

starfish, somesea urchinsin warm seas Most of these animals are sedentary and non-

aggressive and may be avoided if seen andrecognised in time.

The risk is often greater when wading. Someprotection is provided by rubber soled neoprene

diving boots, but hard soled boots are moreeffective.

Venomous octopus Local envenomation at site of bite wound. TheBlue ringed octopusmay on rare Found only in parts of thePacific Oceanfrom Ja
http://en.wikipedia.org/wiki/Jellyfishhttp://en.wikipedia.org/wiki/Jellyfishhttp://en.wikipedia.org/wiki/Jellyfishhttp://en.wikipedia.org/wiki/Sting_rayhttp://en.wikipedia.org/wiki/Sting_rayhttp://en.wikipedia.org/wiki/Sting_rayhttp://en.wikipedia.org/wiki/Lionfishhttp://en.wikipedia.org/wiki/Lionfishhttp://en.wikipedia.org/wiki/Stonefishhttp://en.wikipedia.org/wiki/Stonefishhttp://en.wikipedia.org/wiki/Stonefishhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Blue_ringed_octopushttp://en.wikipedia.org/wiki/Blue_ringed_octopushttp://en.wikipedia.org/wiki/Blue_ringed_octopushttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Pacific_Oceanhttp://en.wikipedia.org/wiki/Blue_ringed_octopushttp://en.wikipedia.org/wiki/Sea_urchinhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Crown_of_thorns_starfishhttp://en.wikipedia.org/wiki/Stonefishhttp://en.wikipedia.org/wiki/Lionfishhttp://en.wikipedia.org/wiki/Sting_rayhttp://en.wikipedia.org/wiki/Jellyfish


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Extremely painful and may result in death. occsions bite a diver. to Australia.

The octopus is unlikely to be aggressive, and is nlikely to bite unless handled. However it can be

camouflaged against the reef and difficult to seenot contacting the reef is the most reliable way t

avoid contact.

Sharks Lacerations by shark teeth can involve

deep wounds, loss of tissue andamputation, with major blood loss. In

extreme cases death may result,

Attack or investigation by shark with

bites. Risk is location, conditions, andspecies dependent.

Consult location-specific information to determirisk.

Never molest even apparently docile sharksunderwater.

Crocodiles Lacerations and punctures by teeth, bruteforce tearing of tissues. Possibility of

drowning.

Crocodiles, in some tropical waters Consult local information on risk. Stay out of waters known to be inhabited by

crocodiles.

Titan triggerfish (description of injury to go here) This tropical Indo-Pacific fish is veryterritorial during breeding season and will

attack and bite divers

Keep a lookout for the fish and move away if they actaggressively.

Very largegroupers. Bite wounds, bruising and crushinginjuries.[citation needed]

TheGiant grouperEpinephelus

lanceolatus can grow very big in tropical

waters, where protected from attack bysharks. There have been cases of very

large groupers trying to swallowhumans.[45][46][47][48][49]

Get local information on risk. Stay clear of very large specimens. Do not attempt to feed the fish, they may take m

than is offered.

Electric shock Electrical discharge that will startle and

may stun the diver

Defense machanism ofElectric eel, in

someSouth Americanfresh waters Get local information on risk. Do not touch the animals if seen.

Defense mechanism ofElectric ray, insome tropical to warm temperate seas

Do not touch the animal.It is said that some naval anti-frogmandefences use electric shock[citation needed]

Keep out of armed forces areas
http://en.wikipedia.org/wiki/Sharkhttp://en.wikipedia.org/wiki/Crocodilehttp://en.wikipedia.org/wiki/Crocodilehttp://en.wikipedia.org/wiki/Titan_triggerfishhttp://en.wikipedia.org/wiki/Titan_triggerfishhttp://en.wikipedia.org/wiki/Grouperhttp://en.wikipedia.org/wiki/Grouperhttp://en.wikipedia.org/wiki/Grouperhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Giant_grouperhttp://en.wikipedia.org/wiki/Giant_grouperhttp://en.wikipedia.org/wiki/Giant_grouperhttp://en.wikipedia.org/wiki/Sharkhttp://en.wikipedia.org/wiki/Sharkhttp://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-alevizon2000-45http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-alevizon2000-45http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-jacksonville2005-47http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-49http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-49http://en.wikipedia.org/wiki/Electric_shockhttp://en.wikipedia.org/wiki/Electric_shockhttp://en.wikipedia.org/wiki/Electric_eelhttp://en.wikipedia.org/wiki/Electric_eelhttp://en.wikipedia.org/wiki/Electric_eelhttp://en.wikipedia.org/wiki/South_Americahttp://en.wikipedia.org/wiki/South_Americahttp://en.wikipedia.org/wiki/South_Americahttp://en.wikipedia.org/wiki/Electric_rayhttp://en.wikipedia.org/wiki/Electric_rayhttp://en.wikipedia.org/wiki/Electric_rayhttp://en.wikipedia.org/wiki/Frogmanhttp://en.wikipedia.org/wiki/Frogmanhttp://en.wikipedia.org/wiki/Frogmanhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Frogmanhttp://en.wikipedia.org/wiki/Electric_rayhttp://en.wikipedia.org/wiki/South_Americahttp://en.wikipedia.org/wiki/Electric_eelhttp://en.wikipedia.org/wiki/Electric_shockhttp://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-49http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-jacksonville2005-47http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-jacksonville2005-47http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-alevizon2000-45http://en.wikipedia.org/wiki/Diving_hazards_and_precautions#cite_note-alevizon2000-45http://en.wikipedia.org/wiki/Sharkhttp://en.wikipedia.org/wiki/Giant_grouperhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Grouperhttp://en.wikipedia.org/wiki/Titan_triggerfishhttp://en.wikipedia.org/wiki/Crocodilehttp://en.wikipedia.org/wiki/Shark


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Powerfulultrasound (description of injury to go here) It is said that some naval anti-frogman

defences use powerful ultrasound[citation

needed]. Also used for long-range

communication withsubmarines[citation

needed] Most high power sonar is used for

submarine detection and targetacquisition.[citation needed]

Keep out of armed forces areas. Avoid large naval ships' anti-submarine warfare

sonar.

SeeUnderwater Port Security System.

Water contaminated by

infectious aquaticorganisms

Weil's disease Leptospirosis infection (Weil's disease) is

commonly transmitted to humans byallowing water that has been contaminated

by animal urine to come in contact withunhealed breaks in the skin, the eyes, or

with the mucous membranes. Outside oftropical areas, leptospirosis cases have a

relatively distinct seasonality with most of

them occurring in spring and autumn.

Avoid diving in contaminated water. Analyse water before diving if presence of

contaminants is suspected, but type and

concentration is not known.

If it is necessary, and depending on

Documents

List of Diving Hazards and Precautions