Since 1997

​Air Quality Campaign

What is carbon monoxide poisoning ?

Carbon monoxide (CO) is an odourless, colourless and tasteless gas, usually produced by the incomplete combustion of carbon containing compounds.
It is absorbed 200 times more readily by haemoglobin than oxygen is. This reduces the oxygen carrying capacity and can eventually lead to oxygen starvation (hypoxia) and even death. The severity of CO poisoning depends on its concentration in the breathing gas and the exposure time. A long exposure to relatively low concentrations can therefore result in serious CO poisoning.
Diving aggravates the toxicity of CO in that the partial pressure of CO is increased as a function of diving depth. As a result, even low CO levels may become dangerous at depth. The manifestations of CO poisoning often appear or worsen during ascent, however, when the benefit of elevated oxygen partial pressure is lost.
What can the dive centre, club or dive shop do?

Make sure the air inlet from compressors is not located nearby any source of contamination such as motor vehicles or boats (say near the jetty), diesel generators or other gas exhausts, or located downwind from the compressor’s own internal combustion engine exhaust.  Also make sure nobody is allowed to smoke or burn any materials nearby the air inlet.
Make sure the correct compressor oil and filters are used, and regularly check that the air intake hose is not damaged and couplings are not loose (which is usually caused by vibration).
Ensure proper maintenance of the compressor, as excessive wear can lead to overheating and these high temperatures may decompose the lubricating oil into toxic products such as CO.
Regularly check the quality of the air: this can be done by using detector tubes and other non-reusable devices, or with electronic analyzers. Alternatively, and required in some regions, air testing by accredited laboratories can be done.
​How to reduce the risk of CO intoxication during diving?

CO contamination usually originates from two separate mechanisms: (1) the compressor air inlet is exposed to exhaust fumes from a combustion engine such as a petrol or diesel compressor engine, power generator, motor car or boat engine; (2) overheating of the compressor leads to a breakdown of the oil lubricants within the compressor itself with production of CO. Divers therefore need to be sure the air they use is uncontaminated.
Since compressors are used to fill many cylinders, CO contamination can be present in all cylinders filled using the same compressor.

What can the diver do?

  • If using your own compressor, respect the recommendations as stated above.
  • Only obtain air or breathing gas fills from a reputable dive centre, club or dive shop.
  • Ask the air supplier how often they check the quality of their air and if they periodically perform compressor maintenance and have a compressor log.
  • If possible, visually check the location of the air intake of the compressor when getting a cylinder filled at an unknown filling station, especially when on a dive holiday.
  • Avoid smoking immediately prior to the dive as cigarette smoke also contains CO.
  • Check your air cylinder for the presence of CO using a personal CO detector device, especially if you have concerns about the quality of the air supplier or when you cannot determine how the dive cylinders where filled.  While electronic CO detectors may be rather expensive for the single diver, products such as the CO - Pro™, which can detect the presence of CO in the breathing gas, are inexpensive, making them accessible to all divers (you may also contact DANSA for the CO-Pro™ device).
  • Although diving accidents due to CO poisoning are relatively rare, the chances increase wherever safety standards are violated. Remote locations and informal compressor installations pose the highest likelihood for CO contamination. 

The CO - Pro™: A quick and effective way to detect CO in breathing air. If the air is contaminated by CO, the sensor within the balloon will change color. You can discover this and many other safety materials in the online DAN Shop.
Also distributed by DAN Southern Africa

What are the signs and symptoms of CO intoxication?
CO poisoning produces all the typical signs of oxygen starvation, such as: breathlessness, confusion, mental fogginess, weakness and eventually unconsciousness. CO can also cause a severe throbbing headache and a sensation of pressure inside the head, vertigo, nausea and vomiting. Many textbooks list cherry red lips, cheeks and fingernails due to CO binding to haemoglobin. However, these are very late findings and, if absent, should not be used to rule out the presence of CO poisoning.

First Aid & treatment

The diver should stop breathing from the contaminated cylinder and end the dive. The  dive  buddy  can use  their  alternative  air  source  to  provide  the diver with uncontaminated air, although if filled using the same compressor this air supply may also be contaminated.

BLS and 100% oxygen should be  administered  as soon as possible.

Call DAN for medical advice and to arrange transportation to an emergency medical facility (preferably with a hyperbaric chamber) for assessment and appropriate treatment.

Safety is in the Air 

CO is not the only potential contaminant in breathing gas, but it is potentially the most dangerous. Other hazards include: 
  • Carbon dioxide (CO2) in excessive quantities, especially for deeper diving, is a health concern.
  • Oil mist (compressor lubricant) is both a health and a fire hazard.
  • Too much moisture will cause equipment flow and cylinder corrosion issues.
  • Dust is hazardous to both our lungs, as well as to fine regulator parts.
  • And then one might even encounter less frequent but certainly reported contamination from vapour released by cleaning compounds in the environment, methane (CH4) or other compounds presenting health, equipment or fire concerns. 
This all implies some awareness by the diver, diligence by the dive station and knowledge by all.

A ​DAN Southern Africa Safety Campaign