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Your Air, Your Safety: A DAN AP Safety and Awareness Campaign

Campaign Announcement

This article explains the reasoning behind the development of our Air Quality campaign. CLICK HERE

Did You Know?

As recreational divers, the gas we breathe should be approximately 79% Nitrogen and 21% Oxygen (with small amounts of other trace gases). However, potentially dangerous contaminants can be introduced when air is compressed. There are a variety of published Compressed Air Purity Standards and, although there can be some variation in these, differences are not great. What can vary substantially is how well such standards are followed.

In some places, there are regulations in place to encourage air fill stations to regularly check their air purity and period inspections to oversee this. In other places, especially in developing countries where dive operations may be remote, there is little or no external oversight, and sometimes relatively little awareness of the potential pitfalls.

Factors such as compressor placement, intake placement, lubricants and filters used and how often these are replaced, the purity of ambient air, and maintenance and overheating of the compressors was impact air quality from time to time and we rely on air fill stations to monitor and manage these.

As divers, we need to be aware of this and do what we can to ensure that the air we receive is not contaminated.  

What is carbon monoxide (CO) and why is it so dangerous?

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 by haemoglobin, the molecule in red blood cells that carries oxygen. This reduces the Oxygen carrying capacity and can eventually lead to hypoxia and in extreme cases it can also lead to death. In addition to reducing the oxygen supply to body tissues, CO is a poison and has direct toxic effects on parts of the body.

How does CO influence diving Safety?

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 result in serious CO poisoning.

In diving, the partial pressure of CO will increase with depth and even a low concentration of CO contamination, which at normal atmospheric pressure and after a prolonged exposure time would have no toxic effect, will become dangerous with increasing depth. When descending the haemoglobin (the molecule in red blood cells that carries oxygen) can get saturated with CO, impairing its ability to bind with oxygen, but the increased oxygen partial pressure may also result in enough oxygen in the blood keeping cells oxygenated. During the dive, the decreased oxygen transportation (through the haemoglobin) is also partially compensated by the amount of dissolved oxygen in the blood plasma. But during the ascent, when the partial oxygen pressure is reduced, and the amount of dissolved oxygen also reduces, this can lead to hypoxia. This might be the reason why the symptoms of poisoning may become worse during or after ascent.

What are the signs and symptoms of a CO intoxication?

As part of our Air Quality Campaign we’ve looked at what CO is and the impact it has on diving safety. But to put it into perspective, and for you to determine whether you may have previously dived with bad air, let’s look at some typical signs and symptoms of carbon monoxide (CO) poisoning:

  • Headache
  • Confusions, memory loss, apathy, drowsiness
  • Dizziness
  • Nausea
  • Vomiting
  • Vertigo
  • Breathlessness with exertion
  • Paralysis and/or Unconsciousness

How do we reduce the risk of CO intoxication during diving?

As we progress with our Air Quality campaign we can see just how serious the issue is. Obviously, we all want to reduce any risk of suffering CO poisoning during diving, but how can we achieve this?

CO contamination usually arises from impurities in the air taken into the compressor or from contaminants generated by the compressor itself. The air compression process can introduce large amounts of CO and CO2 to your breathing air when they are directly available in the environment of the compressor. Therefore, it is important to make sure to check the compressor that fills your air cylinders and the location of its air intake. Let us go a little bit more into detail and find out what you can do to prevent CO intoxication, whether you are the person filling the air cylinders or whether you are the diver using them.

What can Dive Centres, Clubs or Dive Shops do to reduce the risk of CO contamination?

  • Make sure the compressor is placed in a well-ventilated position to reduce over-heating.
  • Make sure the air inlet from the compressor is not located near any source of contamination.
  • Make sure the correct compressor oil and filters are used and change when required; and regularly check that the air intake hose is not damaged and couplings are not loose.
  • 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 analysers. Alternatively, and required in some regions, air testing by accredited laboratories can be done.

What can Divers do to avoid Co Contamination?

  • If using your own compressor, respect the recommendations.
  • Only obtain air or breathing gas fills from a reputable dive centre or dive shop.
  • Ask the air supplier how often they check the quality of their air and if they regularly perform compressor maintenance and have a compressor log.
  • If possible, 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.
  • Check your air cylinder for the presence of CO using a personal CO detector device.
  • Don’t breathe air that has an unpleasant or ‘oily’ odour or taste.

Although diving accidents due to CO poisoning are relatively rare, the chances increase wherever safety standards are violated. Remote locations with little regulation and informal compressor installations pose the highest likelihood for CO contamination.

How Good is Your Gas?

Download our mini-poster with facts, common indicators of breathing bad air, and tips to protect yourself from bad gas.

Scuba Air Quality - Articles by DAN's Francois Burman

Part 1: What do the limits really mean? In this first of two parts, the rationale behind set contaminant limits for acceptable scuba air quality is explained. READ MORE

Part 2: How do we analyse the air we are breathing? In part 2, Francois looks at common contaminants and the various testing options available to dive operators, filling stations and individual divers. READ MORE