The dangers encountered with incorrect breathing air processing

For divers, high concentrations of carbon monoxide, carbon dioxide, oil and water in the breathing air definitely are dangerous. Unpleasant however relatively harmless on the long-term are symptoms such as headache, dizziness and an oily taste in the mouth. However, in worse case scenario intoxication with high concentrations of these substances can and will lead to lethal consequences. Therefore, pay attention to the DIN EN 12021 requirements as mentioned underneath.

Carbon monoxide

This colourless and odorousless gas stops the bond of oxygen to the blood, thus causing an insufficient transport of oxygen towards all vital organs. This can and will cause headache, dizziness, nausea, unconsciousness and even heart failure. Even breathing in small doses under 0.01 vol.% (100 ppm) may cause chronic illness of the heart and nerves. Doses of 0.1 vol.% (1000 ppm) and higher are fatal after prolonged inhalation. (DIN EN 12021 requirement: < 15 ppm)

Carbon dioxide

Carbon dioxide is a natural component of air in very small concentrations. However, in higher doses it leads to breathing limitation and even respiratory arrest. The air breathed in containing too high concentrations of carbon dioxide accelerates heartbeat, increases blood pressure and causes shortness of breath and unconsciousness from a concentration of approximately 5 vol.% (50.000 ppm). Concentrations from 8 vol.% (80.000 ppm) can and will lead to lethal consequences within 30 to 60 minutes. (DIN EN 12021 requirement: < 500 ppm)


In case residual oil in the breathing air is distinctly above the limit value, then the diver notices an oily or stale taste. In addition to acute irritation with coughing and breathing difficulties, nausea and vomiting are likely to occur. The oily mixture can form a permanent deposit in the lungs and thus damage the tissue when frequently inhaled. (DIN EN 12021 requirement: < 0.5 mg/m3)


In case humidity is not completely removed from the compressed air the breathing regulator may ice over when diving in colder waters, thus becoming life threatening situation. The humidity and the coldness produced whilst compressed air is expanding may cause seizure of the 1st stage (pressure reducer) of the breathing regulator due to icing over which may result in uncontrolled blowing or even complete interruption of the air supply. (DIN EN 12021 requirement: < 25 mg/m3)