Sight Search

Scuba Air Quality Part 2

In this part, we look at common contamination and the various testing options available to dive operations, filling stations and individual divers.

In Part 1 on this topic, we discussed the contaminants we are concerned about, how to determine appropriate limits for these contaminants and we noted that the South African regulations have become a little less clear on this subject, pending a revision of SANS 532.
We know that sophisticated laboratories are able to test air for practically any constituent let alone the wide array of potential contaminants. However, to be practical, the measurements need to be performed real-time, on-site and should be limited to those contaminants that are both likely to be entrained and harmful if present. Otherwise, by the time a laboratory report comes back, many cylinders might already be filled with some undesirable or unsafe pollutant.
In Part 2 of this series, we will look at how we actually determine the level of contaminants in our compressed breathing air. We will review the available techniques for the various constituents and common contaminants and then we will discuss field testing options that are available to dive operators, filling stations or even individual divers filling their own cylinders or wishing to test their breathing gas before use. Finally, we conclude with what we can do when test results approach or exceed the set limits of safety and quality.

What Are The Usual Analysis Techniques?

The available analytical methods range from very basic, inexpensive, field testing devices to very sophisticated laboratory equipment. Most of the time, the former is enough to ensure that the compressors and filter packages are working within specification without excessive pollutants being entrained from the surrounding environment. Lower testing costs also encourage more frequent testing, which is more important in an operational setting. Usually, highly-accurate laboratory methods are reserved for forensic or accident investigations. As scuba divers, however, we do need to have some idea of how to assess the “usual suspects” of CO², CO, water vapour and oil. The table below summarises the various field-testing options versus accuracy tradeoffs. Basically, with the exception of the detection of oil, the other stated contaminants can be field tested either using once-off detector tubes or using an electronic analyser.

 In addition to the common contaminants, there is a range of other potential toxic and debilitating compounds that may enter scuba cylinders during filling. Awareness of “environmental” hazards is therefore essential and may include cleaning, industrial or even more natural compounds (such as methane produced by cows).

What Are Our Guiding Limits?

Physiological safe limits for gas contaminants are determined by their partial pressure according to Dalton’s Law. Therefore, the concentration (i.e. fgas) must be considered in relation to the maximum diving depth (i.e. the ambient pressure or Pamb). Air diving is restricted to 50 m and therefore surface equivalent values (i.e. the maximum concentration as measured at 1 ATA that would not be toxic at 6 ATA).

The limits represented in the Contaminant Safe Limits table indicate the effect on human physiology (health). In the case of oil, methane (CH4) or moisture (H²O), the limiting factors are determined by fire risks and risks to equipment.

What Are The Field Testing Options Available To Us?

Irrespective of whether you are testing the gas in a scuba cylinder or the gas delivered by a filling station, there are three fundamental ways to determine air quality:
  • Single-use detector tubes
  • Electronic sensors
  • Laboratory analysis
None of these are cheap, but health and safety are at stake. This means that in the end, an appropriate compromise must be made between convenience, cost and accuracy.

Detector tubes and other non-reusable indicating devices

This is the age-old, tried and tested method. It is relatively simple, but not entirely fool-proof and there is always some degree of uncertainty. In recent years it has become a bit more user-friendly and the accuracy is quite acceptable as shown in the first table (Typical Field Analysers). In simple terms, detector tubes are chemical reagents that are exposed to a given sample (i.e. quantity or volume) of the gas to be tested. Depending on how much of the reagent becomes discoloured as the volume of gas is passed through it, an assessment of the concentration of contaminant can be made. Detector tubes offer a visual indication of the level of contamination; easily read by even the untrained eye.

The tools needed to conduct this in the field may be as simple as some silicon tubing, a few basic flow-meters, a stop-watch and the detector tube; more sophisticated and less “hands-on” devices are available too – at a price.

The new CO-Pro device, soon to be made available through DAN and some dive shops, will be an inexpensive and user-friendly “safety indicator” that can be packed into the travelling diver’s luggage without any space or safety concerns.
Electronic analysers

With the increased use amongst recreational divers of nitrox and other blended gases, we have seen a host of hand-held oxygen and even helium analysers enter the market. Prices in real-terms have come down pretty dramatically over the past 10 years, as popularity and application have increased. Driven primarily by safety concerns, contaminant analysers have entered our market in the same way, with prices dropping steadily: Simple-tooperate, hand-held versions of CO and CO2 analysers are now coming within the reach of individual divers. There are even products entering the fray that combine these with oxygen, moisture and helium, but these are still too expensive for the average travelling diver.

What we would really like to see is that our scuba filling stations invest in some of these instruments, so that regular spot checks can be made on CO, CO2 and moisture levels during everyday fills. Oil vapour assessments are still a bit finicky for real-time use although at least one US-based air quality analysis company has a product that can be used on-site. Located at the local scuba-filling facility, this device communicates with the company’s laboratory over the internet and produces a result in real time that includes oil vapour determination.
Sending a sample to an accredited air-testing laboratory

Lastly, we have a variant of the analytical method used for a highly-accurate determination of gas constituents and contaminants: ready access to a special testing laboratory for breathing gases. While not easily accessible in Southern Africa – given the high courier or postage fees – this style of assessment is popular in Europe and the US. Many dive centres make use of this service by sending in specially-prepared and easy-to-conduct test samples for their quarterly or semi-annual air quality tests. A simple process then captures the “quality” of the air on a specific date and this is then sent in to a sophisticated testing laboratory. Results are sent back via email or mail. Very effective, although the results usually only appear around seven to 10 days after the sample was taken. This option is excellent for routine assessments or for a diving accident investigation, but it does not address the concerns of a dive customer who is not happy with the “smell” or “taste” of the air in their cylinder!

For facilities using this method, we would recommend that they ask for the actual contaminant values rather than just a pass or fail certificate. This would enable the facility to monitor trends or changes in breathing air quality, which in turn might prompt timely filter changes or compressor maintenance before air quality becomes unacceptable.

For the greatest level of confidence, filling stations should be well-managed with regular air quality tests of which the results are readily visible to prospective customers who are about to buy their life-support gas from them. However, dive operations are rarely ideal settings and as we travel the diving regions of the world, this becomes readily apparent in more isolated and less developed parts of the globe. CO, moisture, CO2 and oil often exceed the safety limits, and environmental hazards like methane (CH4) and nitrogen oxides (NOx) become a real concern. Costs are of course an important aspect in deciding which of the three methods to employ.

The individual, safety-conscious diver who has been alerted to reported incidents in certain dive spots might well choose to invest in a CO-Pro, disposable detecting device or even a hand-held electronic CO monitor, ready for the day when they are concerned about their cylinder contents. This is not a significant investment all things considered and certainly better than the complications!

The quality conscious scuba-filling facility has a wider choice and a simple assessment of ongoing sampling costs (on-site or by laboratory) versus an on-site electronic, real-time analyser would be the way to make the sensible decision.

What Do We Do If the Levels Approach Or Exceed The Safe Limits?

The second table (Contaminant Safe Limits) provides an overview of the safe, regulated and ultimately, desired limits. Where regular testing shows that air quality is approaching these limits, there are two options:
  • If it is CO, CO2 or some environmental pollutant that is on the rise, the compressor intake may need to be moved or secured away from the source of pollution.
  • If it is primarily oil, moisture or an associated odour, the compressor and its filtration package should be assessed to decide whether the current maintenance or change-out intervals are adequate. (Note: CO can also be the product of an over-heated compressor.)
Air filtration is a topic for another day, but we do know that as a general rule moisture, oil and CO can and should be removed by the filtration package, whereas CO2 will pass through without any real reduction in level. If the filtration system is not coping, it may be time to consider investing in one of our industry’s recent and long overdue developments: a high-pressure refrigerant dryer. The upfront cost is quickly amortised through a significant reduction in filter replacements. Better still, there will be greater assurance of the highest quality air when it comes to oil and moisture control.

A Final Note

A recent assessment of the quality of scuba air in South Africa concluded that, as a general rule, our local scuba filling stations are doing a pretty good job. This provides some assurance closer to home, but all bets are off when travelling to remote locations. Still, by simply being more aware of the relevant issues, together with an eye on product developments, divers can make better choices on what to expect, what to ensure and what to measure before sinking below the surface on oxygen-enriched exhaust fumes. Jokes aside, sub-standard air can be harmful and even fatal as was reported extensively in the media during 2012.

Science and technology have brought both knowledge and tools within our reach; we should avail ourselves of both and give ourselves a little more assurance and security.

Related Posts


J. de Kooker - November 22nd, 2016 at 11:09pm

Thanks for this article it is very informative and a good eye - opener. I work with automatic gas extinguishing and are well aware of the composition of air and how easilly one can get killed if rules are not applied. A nother thing that bothers me is rusted cylinders and if any studies was or has been conducted with tegards to the inhaling of rust when cylinders are poorly treated and maintained. I experienced this with one of the very prominent holiday resorts. When servicing my equipment I found rust in the first stage as well as the hoses was coated internally with rust I will apreciate your valued input with the afore-mentiond. Kind Regards; Joshua de Kooker ( DAN Member 718005 )


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 DivingSeasickness Prevention and TreatmentMember to Member: Guidelines for SeniorsHigh-Pressure OphthalmologyOver-the-Counter Medications
immersion and bubble formation Accidents Acid reflux Acute ailments After anaesthesia Air Quality Air exchange centre Air hose failure Air supply Airway control Air Alert Diver Magazine Alternative gas mix Altitude changes Altitude diving Altitude sickness Aluminium Oxide Ama divers Amino acids Anaerobic Metabolism Animal life Annual renewal Apnea Apnoea Aquatic life Archaeology Arterial gas embolism Arthroscopic surgery Aspirin Aurel hygiene BCD BHP BLS BWARF Back adjustment Back pain Back treatment Backextensors Badages Bag valve mask Bahamas Balancing Bandaids Barbell back squat Barometric pressure Barotrauma Basic Life Support Batteries Bench press Benign prostate hyperplasia Benzophenones Beth Neale Biophysics Black Blood flow Blood thinners Blue Wilderness Blurred vision Boat safety Boesmans gat Boesmansgat Bone fractures Bouyancy compensators Boyle's Law Boyle\'s Law Bradycardia Brain Breast Cancer Breath Hold Diving Breath holding Breath hold Breath-hold Breathing Gas Breathing gas contamination Breathing Breathold diving Bright Bank Broken bones Bruising Bubbleformation Buddy Exercise Buddy checks Buoyancy Burnshield CGASA CMAS CO2 COVID-19 Updates COVID-19 COVID CPR Cabin pressure Caissons diseas Camera equipment Camera settings Cameras Cancer Remission Cancer treatments Cancer Cannabis and diving Cannabis Cape Town Dive Festival Cape Town Dive Sites Cape Town CapeTown Carbon Monoxide Carbon dioxide Cardio health Cardiological Cardiomyopathy Caribbean Cave diving Chamber Safety Chamber science Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Children diving Chiropractic Chlorophll Christina Mittermeier Citizen Conservation Cleaning products Coastalexcursion Cold Water Cold care ColdWater Cold Commercial diving Commercial schools Composition Compressed Air Compressed gas Consercation Conservation Photographer Conservation photography Conservation Contact lenses Contaminants Contaminated air Coral Conservation Coral Reefs Coral Restoration Coral bleaching CoralGroupers Corals Core strength Corona virus Coro Courtactions Cristina Mittermeier Crohns disease Crowns Crystal build up Crystallizing hoses Cutaneous decompression Cylinder Ruptures Cylinder handwheel Cylinder valves DAN Courses DAN Profile DAN Researchers DAN medics DAN members DAN report DCI DCS Decompressions sickness DCS theories DCS DEMP DM training DNA DReams Dalton's Law Dalton\'s Law Dalton\\\'s Law Dalton\\\\\\\'s Law Dalton\\\\\\\\\\\\\\\'s Law Danel Wenzel Dauin island Dean's Blue Hole Dean\'s Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression illsnes Decompression treatment Decompression Decorator crabs Deep diving Deep water exploration Deepest SCUBA Dive Delayed Offgassing Dental Dever Health Diaphragms Diopter Diseases Disinfection Dive Chamber Dive Computer Dive Destinations Dive H Dive Industry Dive Instruction Dive Instructor Dive Medical Form Dive Medical Dive Practices Dive Pros Dive Research Dive South Africa Dive Training Dive Travel Dive accidents Dive buddies Dive computers Dive courses Dive excursions Dive exercise Dive fitness Dive gear Dive heallth Dive health Dive medicals Dive medicines Dive medicine Dive operators Dive planning Dive safety 101 Dive safety Dive safe Dive staff Dive travels DiveLIVE Diveleader training Diveleaders Diver Health Diver Profile Diver infliencers Diver on surface Divers Alert Divesites Diving Divas Diving Kids Diving Trauma Diving career Diving emergencies Diving emergency management Diving fit Diving guidelines Diving injuries Diving suspended Diving Dizziness Dolphins Domestic Donation Dowels Dr Rob Schneider Drift diving Drysuit diving Drysuit valves Drysuits Dyperbaric medicines EAPs EAP Ear pressure Ear wax Ears injuries Eco friendly Education Electronic Emergency action planning Emergency decompression Emergency plans Emergency underwater Oxygen Recompression Emergency Enviromental Protection Environmental factors Environmental impact Environmental managment Equalisation Equipment care Equipment failure Equipment inspection Evacuations Evacuation Evaluations Even Breath Exercise Exhaustion Extended divetime Extinguisher Extreme treatments Eye injuries FAQ Factor V Leiden Failures FalseBay Diving Fatigue Faulty equipment Female divers Fetus development Fillings Fire Coral Fire Safety Firefighting First Aid Equipment First Aid Kit First Aid Training First Aid kits Fish Identification Fish Life Fish Fit to dive Fitness Training Fitness to dive Fitness Flying Focus lights Fractures Francesca Diaco Francois Burman Fredive Free Student cover Free diving Free flow Freedive INstructor Freedive Training Freediver Freediving Instructors Freediving performance Freediving Gas Density Gas consumption Gas laws Gas mixes GasPerformance Gases Gass bubbles Gastoeusophagus Gastric bypass Gastroenterologist Gear Servicing Germs Geyer Bank Gordon Hiles Great White Sharks Guinness World Record Gutt irritations HCV HELP HIRA HMLI HMS Britanica Haemorhoid treatment Hazard Description Hazardous Marine life Hazardous marinelife Health practitioner Heart Attack Heart Health Heart Rate monitor Heart fitness Heart rates Heart rate Heart Heat stress Helium Hepatitis C Hepatitus B High Pressure vessels High temperatures Hip strength Hip surgery Hippocampus History Hot Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hygiene Hyperbaric Chamber Hyperbaric research Hyperbarics Hypothermia Hypoxia IdentiFin Imaging Immersion Immine systems In Water Recompression Indemnity form Indian Ocean Indonesia Inert gas Infections Infra red Imaging Injections Instinct Instruction Instructors Insurance Integrated Physiology International travel International Interval training Irritation Isotta housing Joint pain Junior Open Water Diver KZN South Coast Karen van den Oever Kate Jonker KateJonker Kidneys Kids scubadiver Komati Springs KwaZulu Natal Labour laws Laryngospasm Lauren Arthur Learning to dive Legal Network Legal advice Legislation Lenses Leukemis Liability Risks Liability releases Liability Life expectancy Lifestyle Lightroom editing Live aboard diving Liver Toxicity Liver diseas Liz Louw Low blood pressure Low pressure deterioration Low volume masks Lung Irritation Lung function Lung injuries Lung squeeze Lung surgery Lung MOD Macro photography Maintenance Malaria Mammalian Dive Response Mammalian effect Marine Biology Marine Scientists Marine conservation Marine parks Marinelife Masks Master scuba diver Maximum operating depth Medical Q Medical emergencies Medical questionaire Medical statement Medicalresearch Medication Mehgan Heaney-Grier Mermaid Danii Mesophotic Middle ear pressure Mike Bartick Military front press Mixed Gas Mono Fins Mooring lines More pressure Motion sickness Mozambique Muscle pain Mycobacterium marinum National Geographic Nausea Nautilus Neck pain Neuro assessments Neurological assessments Nitrogen Narcosis Nitrogen build up Nitrox No-decompression Non-nano zinc oxide Non-rebreather Mask Nonrebreather masks Normal Air Nosebleeds Nuno Gomes O2 providers O2 servicing OOxygen maintenance Ocean Research Ocean pollution Oil contamination Open water divers Optical focus Orbital implants Oronasal mask Osteonecrosis Out and about Out of air Outreach Oxygen Administration Oxygen Cylinder Oxygen Units Oxygen deficit Oxygen deicit Oxygen dificiency Oxygen ears Oxygen equipment Oxygen masks Oxygen supplies Oxygen supply Oxygen systems Oxygen therapy Oxygen P J Prinsloo PADI Freedivers PFI PJP Tech Parentalsupervision Part 3 Partner Training Perspective Philippine Islands Philippines Phillipines Photographers Photography tips Photography Physioball Physiology Physiotherapy Pills Pistons Planning Plastic Pneumonia Pneumothorax Poison Pollution Pool Diving Pool workout Post-dive Pre-dive Predive check Pregnancy Pregnant divers Preparation Prepared diver Press Release Preventions Professional rights Provider course Psycological Pulmanologist Pulmonary Bleb Pulmonary Edema Pulse Punture wounds Pure Apnea Purge RAID South Africa RCAP REEF Radio communications Range of motion Rashes Rebreather diving Rechargeable batteries. Recompression chamber Recompression treatment Recompression Recycle Reef Conservation Reef safe Reef surveyors Refractive correction Regulator failure Regulators Regulator Remote areas Renewable Report incidents Rescue Divers Rescue Procedure Rescue breathing Rescue breaths Rescue training Rescue Resume diving Return To Diving Return to diving Risk Assessments Risk assesments Risk assessment Risk elements Risk management Roatan Marine Park Roatan SABS 019 SafariLive Safety Stop Safety SaherSafe Barrier Salty Wanderer Sanitising Sara Andreotti Saturation Diving Save our seas Science Scombroid Poisoning Scuba Air Quality Scuba Injury Scuba Instructor Scuba children Scuba dive Scuba health Scubalearners Scubalife Sea Horses Sealife Sea Shark Protection Shark Research Shark conservation Shark diving Sharks Shoulder strength Sideplank Signs and Symptoms Sit-ups Skin Bends Skin outbreak Skin rash Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands Sonnier bank South Africa Spinal bends Spinal cord DCS Spinal pain Splits Squeezes Stability exercise Standars Stay Fit Stents Step ups Stephen Frink Stepping up Strobe Lighting Stroke Submerge tech Submerged Sudafed Sulawesi Sun protection Sunscreen Supplemental oxygen Surface supplied Air Surfaced Surgeries Surgery Suspension training TRavel safety Tabata protocol Talya Davidoff Tattoes Technical Diving Technical divng The Bends The truth Thermal Notions Tides Tips and trick Tooth squeeze Transplants Travel smarter Travel tips Travel Tropical Coastal Management Tunnelling Tweezers Ultrsound Umkomaas Unconsciousness Underground work Underwaater Photos Underwater floral Gardens Underwater hockey Underwater photographer Underwater photography Underwater pho University of Stellenbosch Urinary retention. Vaccines Vagus nerve Valsalva manoeuvers Valve stem seals Vape Vaping Vasopressors Vasvagal Syncope Venting Verna van Schak Virus infections Volatile fuels Washout treatments Wastewater Watchman device Water Resistance Water Weakness Weigang Xu Weights West Papua Western Cape Diving Wet diving bell Wetsuit fitting Wetsuits White balance Wide angles Wildlife Winter Wits Underwater Club Woman in diving Womans health Woman Women In Diving SA Women and Diving Women in diving Womens health Work of Breathing Workout World Deeepst Dive Record World Records Wound dressings Wreck divers Wreck dive Wreckdiving Wrecks Yoga Youth diver Zandile Ndholvu Zoology abrasion acoustic neuroma excision adverse seas air-cushioned alert diver altitude anemia antibiotics anticoagulants antiseptics bandages barodontalgia bent-over barbell rows bioassays body art breathing air calories burn carbon dioxide toxicity cardiovascular cerebrospinal fluid checklist chemo port children child clearances closed circuit scuba corrective lenses currents cuts dead lift decompression algorithms decongestants decongestion dehydration dive injuries dive medicing dive ready child dive reflex dive tribe diver in distress diver rescue diver training dive diving attraction doctors domestic travel dri-suits drowning dry mucous membranes dry suits dry e-cigarettes ear spaces elearning electrolyte imbalance electroytes emergency action plans emergency assessment emergency training environmentally friendly equalising equalizing exposure injuries eyes fEMAL DIVERS fire rescue fitnes flexible tubing frediving freedivers gas bubble gas poisoning gastric acid gene expression health heartburn histidine hospital humidity immersion and bubble formation immersion pulmonary edema (IPE jaundice join DAN knee longevity lower stress malaise marielife marine pathogens medical issues medical procedures medical risk assesment medications mental challenge mental preparedness micro-organisims micro minor illness mucous membranes nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles off-gassed operating theatre operations orthopeadic outgas pain perforation phillippines physical challenges pinched nerves plasters polyester-TPU polyether-TPU post dive posture prescription mask preserve prevention psychoactive pulmunary barotrauma rebreather mask rebreathers retinal detachment risk areas safety stops saturation scissors scuba equipment scuba single use sinus infections smoking snorkeling. spearfishing sterilising stings strength sub-aquatic sunscreen lotion swimmers ears tattoo care tecnical diver thermal protection tissue damage toxicity training trimix unified standards upwelling vision impaired warmers water quality zinc oxide