Preventing Breathing-Gas Contamination

Incidents involving bad breathing gas — be it air, nitrox, trimix or another mixture — are rare, yet they do occur. Health effects on divers vary depending on the contaminant breathed. Among the most severe symptoms of breathing contaminated gas are impaired judgment and loss of consciousness, both of which may be deadly underwater.
Sources of contamination include hydrocarbons from compressor lubricants, carbon monoxide (CO) from engine exhaust (or overheated compressor oil) and impurities from the surrounding environment such as methane and carbon dioxide (CO2). Dust particles in breathing gas can also be hazardous, potentially impairing respiratory function or damaging diving equipment. Excessive moisture can cause corrosion in scuba cylinders and other dive gear and may cause regulators to freeze due to adiabatic cooling (heat loss subsequent to increased gas volume).
Sources of contamination include hydrocarbons from compressor lubricants, carbon monoxide (CO) from engine exhaust (or overheated compressor oil) and impurities from the surrounding environment such as methane and carbon dioxide (CO2). Dust particles in breathing gas can also be hazardous, potentially impairing respiratory function or damaging diving equipment. Excessive moisture can cause corrosion in scuba cylinders and other dive gear and may cause regulators to freeze due to adiabatic cooling (heat loss subsequent to increased gas volume).

Recommendations for Compressor Operators
Compressor operators can help prevent gas contamination and mitigate the risk of dive accidents in several ways.
Attentive compressor maintenance. Proper compressor maintenance helps ensure breathing-gas quality as well as extends the life of the compressor. Breathing-gas contamination is less likely in well-maintained and properly functioning compressors. If maintenance is neglected and the compressor overheats, the lubricating oil may break down and produce CO and other noxious byproducts.
Effective procedures. A fill checklist can help ensure safety procedures are remembered when cylinders are filled. Before starting to fill tanks, the operator should inspect the compressor's filters for damage and note the presence of contaminants such as cigarette smoke, paint fumes or engine exhaust near the intake. If the operator notes any chemical or oily odors after filling has started, he should shut down the compressor immediately. Other useful strategies for reducing the risk of gas contamination include keeping records of air fills and maintenance, ensuring operator qualifications are up to date, using proper oil and filters, and maintaining a clean and organised tank-filling room.
Air-quality testing. As a diver descends and ambient pressure increases, the amount of gaseous contaminants breathed also increases. This explains why a contaminated gas that is not toxic at the surface may be at depth. Breathing gas must be tested for a variety of contaminants both regularly and continuously to ensure compliance with diving-adjusted contaminant levels.
Compliance with breathing-gas quality standards is not strictly enforced, and most of the responsibility for testing lies with the operator. Several methods of testing are available to compressor operators, and they vary in price and complexity. Continuous CO-monitoring devices include electrochemical sensors with colour indicators. Devices that continuously monitor moisture level are also available. Operators can send a breathing-gas sample to an accredited laboratory for analysis of oxygen, CO, CO2, moisture, oil/hydrocarbons and even particulate matter; this is recommended on a quarterly basis.
Air Quality Specifications for Recreational Diving
Compressor operators can help prevent gas contamination and mitigate the risk of dive accidents in several ways.
Attentive compressor maintenance. Proper compressor maintenance helps ensure breathing-gas quality as well as extends the life of the compressor. Breathing-gas contamination is less likely in well-maintained and properly functioning compressors. If maintenance is neglected and the compressor overheats, the lubricating oil may break down and produce CO and other noxious byproducts.
Effective procedures. A fill checklist can help ensure safety procedures are remembered when cylinders are filled. Before starting to fill tanks, the operator should inspect the compressor's filters for damage and note the presence of contaminants such as cigarette smoke, paint fumes or engine exhaust near the intake. If the operator notes any chemical or oily odors after filling has started, he should shut down the compressor immediately. Other useful strategies for reducing the risk of gas contamination include keeping records of air fills and maintenance, ensuring operator qualifications are up to date, using proper oil and filters, and maintaining a clean and organised tank-filling room.
Air-quality testing. As a diver descends and ambient pressure increases, the amount of gaseous contaminants breathed also increases. This explains why a contaminated gas that is not toxic at the surface may be at depth. Breathing gas must be tested for a variety of contaminants both regularly and continuously to ensure compliance with diving-adjusted contaminant levels.
Compliance with breathing-gas quality standards is not strictly enforced, and most of the responsibility for testing lies with the operator. Several methods of testing are available to compressor operators, and they vary in price and complexity. Continuous CO-monitoring devices include electrochemical sensors with colour indicators. Devices that continuously monitor moisture level are also available. Operators can send a breathing-gas sample to an accredited laboratory for analysis of oxygen, CO, CO2, moisture, oil/hydrocarbons and even particulate matter; this is recommended on a quarterly basis.
Air Quality Specifications for Recreational Diving

Recommendations for Divers
Ask questions and be observant. If you are unsure about the breathing-gas quality at a fill station, ask questions about compressor maintenance, procedures and testing. Ask if the compressor operator monitors for CO and how often they send samples to a lab for analysis. Look for posted breathing-gas-analysis reports, and note whether the fill room is clean, organized and well ventilated. Observe the proximity of the compressor intake to sources of exhaust, and look to see whether the compressor has an hour meter that can be monitored for regular maintenance.
Always conduct a predive gas check. If your breathing gas has an unusual odour or taste, do not dive with it — this is a red flag for oil or combustion contamination. However, keep in mind that not all contaminants can be detected this way; CO, for example, is odourless and tasteless. Electronic CO detectors or products such as CO-PROTM can be used to detect the presence of CO in breathing gas. Divers should always use oxygen analysers to determine the level of oxygen in a nitrox mixture to prevent oxygen toxicity.
Confirming Contamination
Ask questions and be observant. If you are unsure about the breathing-gas quality at a fill station, ask questions about compressor maintenance, procedures and testing. Ask if the compressor operator monitors for CO and how often they send samples to a lab for analysis. Look for posted breathing-gas-analysis reports, and note whether the fill room is clean, organized and well ventilated. Observe the proximity of the compressor intake to sources of exhaust, and look to see whether the compressor has an hour meter that can be monitored for regular maintenance.
Always conduct a predive gas check. If your breathing gas has an unusual odour or taste, do not dive with it — this is a red flag for oil or combustion contamination. However, keep in mind that not all contaminants can be detected this way; CO, for example, is odourless and tasteless. Electronic CO detectors or products such as CO-PROTM can be used to detect the presence of CO in breathing gas. Divers should always use oxygen analysers to determine the level of oxygen in a nitrox mixture to prevent oxygen toxicity.
Confirming Contamination

Identifying contamination incidents based on symptoms alone is difficult, as the associated symptoms are often similar to other diving-related and non-diving illnesses. If a diver suspects he was exposed to bad breathing gas, he should seek a medical evaluation and have the gas tested. Observing the health of other divers who had their tanks filled at the same source may be helpful in determining whether a diver's symptoms are related to contamination.
DAN Research
DAN occasionally receives reports of problems from divers breathing contaminated gas, but we suspect this issue is under reported. To encourage divers to report compressed-gas contamination, DAN will assist with gas analysis. If you were involved in an incident possibly related to breathing contaminated gas and you have lawful control of the tank, please preserve the tank and contact DAN Research at +27 828 10 60 10 .
Burman F. Scuba air quality. Alert Diver Southern Africa. Autumn 2013: 14-18.
Millar IL, Moudley PG. Compressed breathing air: the potential for evil from within. Diving and Hyperbaric Medicine. 2008; 38: 145-51.
© Alert Diver — Spring 2014
DAN Research
DAN occasionally receives reports of problems from divers breathing contaminated gas, but we suspect this issue is under reported. To encourage divers to report compressed-gas contamination, DAN will assist with gas analysis. If you were involved in an incident possibly related to breathing contaminated gas and you have lawful control of the tank, please preserve the tank and contact DAN Research at +27 828 10 60 10 .
Burman F. Scuba air quality. Alert Diver Southern Africa. Autumn 2013: 14-18.
Millar IL, Moudley PG. Compressed breathing air: the potential for evil from within. Diving and Hyperbaric Medicine. 2008; 38: 145-51.
© Alert Diver — Spring 2014
Posted in Alert Diver Spring Editions
Tagged with Contaminated air, Breathing Gas, Scuba Air Quality, Compressed gas
Tagged with Contaminated air, Breathing Gas, Scuba Air Quality, Compressed gas
Categories
2021
March
Old Habits Die HardSave a Diver, Save YourselfCylinder SafetyUndercover CrabsReef safe sunscreenPhysics, Biophysics and Decompression SicknessModels and Marine LifeSunscreen and CoralCristina Mittermeier: Commitment to ConservationDiving After a StrokeCurrent DivesThis Bites: Prevention TreatmentEnvironmental Considerations for Disinfection
April
Aqua Pool Noodle ExercisesUnderwater Photographer and DAN Member Madelein Wolfaardt10 Simple Things You Can Do to Improve Your Underwater PhotographyCOVID-19 and Diving: March 2021 UpdateDiver Return After COVID-19 Infection (DRACO): A Longitudinal AssessmentGuidelines for Lifelong Medical Fitness to DiveExperienceFitness Myth or Fitness Fact?The Safety of Sports for Athletes With Implantable Cardioverter-DefibrillatorsCardiovascular Fitness and DivingHypertensionPatent Foramen Ovale (PFO)Headaches and DivingMiddle-Ear Barotrauma (MEBT)O’Neill Grading SystemMask Squeeze (Facial Barotrauma)Sinus BarotraumaInner-Ear Barotrauma (IEBT)Middle-Ear EqualisationAlternobaric VertigoDecompression IllnessOn-Site Neurological ExaminationTreating Decompression Sickness (The Bends)Top 5 Factors That Increase Your Risk of the BendsHow to Avoid Rapid Ascents and Arterial Gas EmbolismUnintended Rapid Ascent Due to Uncontrolled InflationUnexpected Weight LossFlying After DivingWisdom Tooth Extraction and DivingYour Lungs and DivingScuba Diving and DiabetesDiving after COVID-19: What We Know TodaySwimmer’s Ear (Otitis Externa)Motion SicknessFitness for DivingDiving After Bariatric SurgeryWhen to Consult a Health-Care Provider Before Engaging in Physical ActivitiesFinding Your FitnessHealth Concerns for Divers Over 50Risk Factors For Heart DiseaseJuggling Physical Exercise and Diving
2020
January
February
Group Fitness at the PoolHow to Rescue a Distressed diver at the SurfaceHow to manage Near-DrowningNo Sit-ups no problem How to manage MalariaHow to manage Oxygen Deficiency (Hypoxia)What to do when confronted by a sharkHow to manage Scombroid PoisoningHow to perform a Deep Diver RescueHow to perform One-rescuer CPRHow to perform a Neurological Assessment
March
DAN’s Quick Guide to Properly Disinfecting Dive GearCOVID-19 : Prevention Recommendations for our Diving CommunityGermophobia? - Just give it a reasonable thoughtScuba Equipment care – Rinsing and cleaning diving equipmentCOVID-19 and DAN MembershipFurther limitations imposed on travels and considerations on diving activitiesDAN Membership COVID-19 FAQsLancet COVID-19 South African Testing SitesCOVID-19 No Panic Help GuideGetting Decompression Sickness while FreedivingDown in the DumpsCardiovascular Disease and DivingDelayed Off-GassingDiving after Dental surgeryDiving with Multiple MedicationsPygmy Seahorses: Life AquaticAfrica DustCOVID-19 Myth BustersScuba Units Are Not Suitable Substitutes for VentilatorsDisinfection of Scuba Equipment and COVID-19Physioball Stability Exercises
April
COVID-19 AdvisoryScuba Equipment Care - Drying & Storing Your GearTransporting Diving Lights & BatteriesHow to Pivot Your Message During a CrisisTourism Relief FundCOVID-19 Business Support ReviewDiving After COVID-19: What We Know TodayEUBS-ECHM Position Statement on Diving ActivitiesPart 2: COVID-19 Business Support ReviewPress Release
May
Diving in the Era of COVID-19Dive Operations and COVID-19: Prepping for ReturnCOVID-19 & Diving Activities: 10 Safety RecommendationsCOVID-19: Surface Survival TimesThe Philippines at its FinestThe Logistics of ExplorationThe Art of the Underwater SelfieShooter: Douglas SeifertFAQs Answered: Disinfecting Scuba EquipmentStock your First-Aid KitResearch and OutreachCovid-19 ResearchOut of the BlueEffects of Aspirin on DivingThe New Pointy end of DivingDiving and Hepatitis CCaissons, Compressed-Air work and Deep TunnellingPreparing to Dive in the New NormalNew Health Declaration Form Sample Addressing C-19 IssuesDiving After COVID 19: What Divers Need to Know
June
Travel Smarter: PRE-TRIP VACCINATIONSAttention-Deficit/Hyperactivity Disorder and DivingCOVID-19: Updated First Aid Training Recommendations From DANDiving with a Purpose in National Marine SanctuariesStay Positive Through the PandemicFor the Dive Operator: How to Protect Your Staff & ClientsStudying Deep reefs and Deep diversAsking the Right QuestionsLung squeeze under cold diving conditions
July
Dive DeprivationVolunteer Fish Surveys: Engage DiversDAN Member Profile: Mehgan Heaney-GrierTravel Smarter: Don’t Cancel, Reschedule InsteadDive Boat Fire SafetyRay of HopePartner ExercisesDiving at AltitudeAluminium ExposureHip FracturesAcoustic NeuromaGuidelines for Lifelong Medical Fitness to DiveNew Dive Medical Forms
August
Women in Diving: Lauren Arthur, Conservationist & Natural History Story TellerWomen in Diving: Dr Sara Andreotti White Shark ResearcherTiming ExerciseWomen in Diving: The Salty Wanderer, Charlie WarlandWomen in Diving: Beth Neale, Aqua soul of freedivingWomen in Diving: Diving and spearfishing Diva, Jean HattinghWomen in Diving: Zandile Ndhlovu, The Black Mermaid
September
October
Freediving For ScienceStep Exercises with CardioFluorescence Imaging help Identify Coral BleachingChildren and DivingThe Watchman device and divingScuba Diving and Factor V Leiden gene mutationNitrogen Narcosis at shallow depthsOil and Particulates: Safe levels in Breathing Air at depthDive Principles for Coping with COVID-19The Importance of a Predive Safety CheckTalya Davidoff: the 'Plattelandse Meisie' Freediver
2019
February
April
May
DAN Press ReleaseYour Dive Computer: Tips and tricks - PART 1Your Dive Computer: Tips and tricks - PART 2Aural HygieneDCS AheadHow Divers Can Help with coral conservationRed Tide and shellfish poisoningDiving after Kidney DonationDiving with hypertrophic cardiomyopathyEmergency Underwater Oxygen Recompression
June
July
September
October
November
Exercise drills with DowelsHeart-rate TrainingCultivating ConservationTRavel Smarter : Evaluating an unfamiliar Dive operatorChallenging the Frontiers of Decompression ResearchTravel Smarter: Plan for Medical EmergenciesWhen should I call my Doctor?DAN Student Medical Expense CoverageAdvice, Support and a LifelineWetsuits and heat stressDiving after Chiropractic adjustments
2018
April
Flying after pool diving FAQLung squeeze while freediving FAQDiving after Bariatric surgery FAQMarine injuries FAQVasovagal Syncope unpredictable FAQIncident report procedure FAQDiving after knee surgery FAQDiving when in RemissionDive with orbital Implant FAQInert gas washout FAQOxygen ears FAQPost Decompression sicknessChildren and diving. The real concerns.Diving after SurgeryPhysiology of Decompresssion sickness FAQDiving and regular exerciseGordon Hiles - I am an Underwater Cameraman and Film MakerScuba Air QualityBreath-hold diving. Part 3: The Science Bit!Compensation Legislation and the Recreational DiverCape Town DivingFive pro tips for capturing better images in cold waterThe Boat Left Without You: Now What?
May
When things go wrongEmergency Planning: Why Do We Need It?Breath-hold diving: Running on reserve -Part 5 Learning to RebreatheSweet Dreams: When Can I Resume Diving Post Anaesthesia?Investing in the future of reefsTo lie or not to lie?THE STORY OF A RASH AFTER A DIVEFirst Aid KitsTaravana: Fact or Falacy?
June
Oxygen Unit MaintenanceKnow Your Oxygen-Delivery Masks 1Know Your Oxygen-Delivery Masks 2Emergency Oxygen unitsInjuries due to exposure - HypothermiaInjuries due to exposure - Altitude sicknessInjuries due to Exposure - Dehydration and other concernsHow to plan for your dive tripThe Future of Dive MedicinePlastic is Killing our ocean
September
Return to DivingDiagnoses: Pulmonary blebSide effects of Rectogesic ointmentDiving with ChemotherapyReplacing dive computers and BCDsCustomize Your First-Aid KitPlan for medical emergenciesHow the dive Reflex protects the brain and heartDry suits and skin BendsAltitude sickness and DCSScuba Diving and Life Expectancy
2017
March
April
Incident Insight: TriageA Field Guide to Minor MishapsSnorkels: Pros & ConsTime & RecoveryMedication & Drug UseDiving with CancerNitrox FAQCOPD FAQHyperbaric Chamber FAQJet Lag FAQHydration FAQAnticoagulant Medication FAQFluid in the Ear FAQEye Surgery FAQElderly Divers FAQNitrogen FAQHealth Concerns FAQMotion Sickness FAQMicronuclei FAQ
June
August
2016
February
March
Breath-Hold Diving & ScubaReturn to Diving After DCITiming Exercise & DivingHot Tubs After DivingSubcutaneous EmphysemaIn-Water RecompressionDiving at AltitudeFlying After DivingDiving After FlyingThe Risks of Diabetes & DivingFlu-like Symptoms Following a DiveHand & Foot EdemaFrontal HeadachesBladder DiscomfortLatex AllergiesRemember to BreatheProper Position for Emergency CareAches & PainsCell Phones While DrivingSurfers Ear Ear Ventilation TubesDealing with Ear ProblemsDiving with Existing Ear InjuriesPerforated Ear DrumENT SurgeryUnpluggedCochlear ImplantsPortuguese Man-of-WarJellyfish StingsLionfish, Scorpionfish & Stonefish EnvenomationsStingray Envenomation Coral Cuts, Scrapes and RashesSpeeding & Driving Behaviour
June
Newsflash! Low Pressure Hose DeteriorationItching & rash go away & come back!7 Things we did not know about the oceanMigraine HeadacheAttention Deficit Disorder Cerebral Vascular AccidentEpilepsyCerebral PalsyHistory of SeizuresMultiple Sclerosis Head TraumaBreast Cancer & Fitness to Dive IssuesLocal Allergic ReactionsSea LiceHow ocean pollution affects humans Dive Fatality & Lobster Mini-Season StatisticsPregnancy & DivingReturn to Diving After Giving BirthBreast Implants & DivingMenstruation During Diving ActivitiesOral Birth ControlBreast FeedingPremenstrual SyndromeOsteoporosisThe Aftermath of Diving IncidentsCompensation Legislation & the Recreational DiverNoise-Induced Hearing LossLegal MattersThe Nature of Liability & DivingDAN Legal NetworkWaivers, Children & Solo DivingHealthy, but overweight!Taking Medication while Scuba DivingGetting Fit for the Dive SeasonBone Considerations in Young DiversAsthma and Scuba DivingHepatitisDiving with HyperglycemiaShoulder PainDiving After Spinal Back Surgery
August
Hazard Identification & Risk AssessmentCaring For Your People Caring For Your FacilitiesCaring For Your BusinessScuba Air Quality Part 1Scuba Air Quality Part 2Chamber Maintenance Part 1Chamber Maintenance Part 2The Aging Diver Propeller SafetyRelease The PressureDon't Get LostMore Water, Less Bubbles13 Ways to Run Out of Air & How Not To7 Mistakes Divers Make & How To Avoid ThemSafety Is In The AirHow Good Is Your Emergency Plan
2015
January
March