Gaseous Impurities in Compressed Breathing Air or Gas Mixtures for Scuba Diving


Scuba diving, a popular underwater recreational activity and essential tool for underwater research and exploration, relies heavily on the quality of the compressed air or gas mixtures used in divers’ breathing equipment. This entry aims to provide an in-depth analysis of the gaseous impurities, which can contaminate these breathing mixtures, posing potential risks to diver health and safety. Recognizing the potential sources of contaminants and understanding the consequences of exposure to these impurities is crucial for the diving community, both for ensuring safe diving practices and for maintaining the long-term health of divers.

Sources of Gaseous Impurities:

Gaseous impurities in compressed breathing air or gas mixtures can originate from various sources, which include the following:

  1. Contamination of the ambient air: The ambient air used for compression may contain contaminants such as airborne particles, combustion byproducts, and volatile organic compounds (VOCs) from industrial, agricultural, or vehicular emissions.
  2. Inadequate filtration: Inefficient or poorly maintained filters in the compressor system can allow contaminants to pass through, resulting in impure breathing mixtures.
  3. Compressor issues: The compressor itself can be a source of contamination if it produces oil or other lubricant aerosols, which can mix with the compressed air or gas.
  4. Cylinder contamination: Cylinders used to store compressed air or gas mixtures may contain residual contaminants from previous use, corrosion, or manufacturing processes.
  5. Handling and transportation: Contaminants may be introduced during the filling, transportation, or storage of cylinders, particularly if proper handling procedures are not followed.

Types of Gaseous Impurities:

Gaseous impurities in compressed breathing air or gas mixtures can be categorized into several major groups:

  1. Gaseous contaminants: a. Carbon monoxide (CO): A colorless, odorless, and tasteless gas, CO can result from incomplete combustion of hydrocarbon fuels. High levels of CO in breathing mixtures can lead to carbon monoxide poisoning, causing symptoms such as headache, dizziness, nausea, and even death. b. Carbon dioxide (CO2): Elevated levels of CO2 can cause hypercapnia, leading to respiratory acidosis, confusion, unconsciousness, and in severe cases, death. c. Nitrogen oxides (NOx): Generated by combustion processes, exposure to high levels of NOx can lead to respiratory irritation and exacerbate pre-existing respiratory conditions.
  2. Volatile organic compounds (VOCs): VOCs, such as solvents, fuels, and other chemicals, can cause a range of symptoms, from dizziness and nausea to long-term organ damage and cancer, depending on the specific compound and exposure level.
  3. Oil and lubricant aerosols: These contaminants, originating from the compressor, can cause respiratory irritation and long-term lung damage.
  4. Particulate matter: Particles, including rust, dust, and other debris, can cause irritation, abrasion, or infection in the respiratory system.
  5. Water vapor and moisture: Excess water in the compressed air can lead to condensation, promoting the growth of potentially harmful microorganisms and causing corrosion in cylinders and breathing equipment.

Effects of Gaseous Impurities on Diver Health and Safety:

The presence of gaseous impurities in compressed breathing air or gas mixtures can have significant short-term and long-term consequences for divers, including:

  1. Acute health effects: Depending on the type and concentration of the impurity, divers may experience symptoms such as dizziness, headaches, nausea, confusion, respiratory irritation, or unconsciousness.
  2. Chronic health effects: Repeated exposure to certain impurities, such as VOCs and oil aerosols, can lead to long-term health issues, including organ damage, chronic respiratory conditions, and an increased risk of cancer.
  1. Impaired decision-making and performance: The physiological effects of gaseous impurities may impair a diver’s cognitive abilities, motor skills, and reaction times, increasing the likelihood of accidents and incidents during a dive.
  2. Equipment degradation: Corrosion and the accumulation of contaminants within cylinders and breathing equipment can compromise their structural integrity and performance, potentially leading to equipment failure.

Preventive Measures and Standards:

To mitigate the risks associated with gaseous impurities in compressed breathing air or gas mixtures, the diving community has established several preventive measures and industry standards, including:

  1. Air quality standards: Organizations such as the Compressed Gas Association (CGA), European Norms (EN), and the International Organization for Standardization (ISO) have set forth stringent air quality requirements for compressed breathing air and gas mixtures, specifying acceptable limits for various contaminants.
  2. Compressor maintenance: Regular inspection, maintenance, and servicing of compressors, including filter replacement and oil changes, are essential for ensuring the production of clean and uncontaminated breathing mixtures.
  3. Cylinder inspection and cleaning: Cylinders should be visually inspected for signs of corrosion, damage, or contamination before each fill and should undergo periodic hydrostatic testing to assess their structural integrity. Additionally, thorough cleaning and drying procedures should be followed to minimize the risk of contamination.
  4. Proper handling and storage: Adherence to best practices for the filling, transportation, and storage of cylinders can help prevent the introduction of contaminants into the breathing mixtures.
  5. Training and awareness: Divers and dive professionals should be educated on the risks associated with gaseous impurities, the importance of air quality, and the proper procedures for handling and maintaining equipment.


Gaseous impurities in compressed breathing air or gas mixtures pose significant risks to the health and safety of scuba divers. By understanding the sources, types, and effects of these contaminants, as well as adhering to established industry standards and preventive measures, the diving community can help ensure that divers enjoy safe, enjoyable, and healthy underwater experiences.