What types of gases may affect seafarers

  1. Carbon monoxide: it is often mild but may be chronic or frequently recurring; can occur when a person inhales smoke from a large fire or from poorly ventilated internal combustion engines, fuel stoves and heaters.
  2. Carbon dioxide: it is nontoxic but displaces breathable air from enclosed spaces. It is heavier than air and accumulates at the bottom of enclosed spaces.
  3. Cyanide: it is used to fumigate ships. Exposure can occur if fumigation is carried out carelessly or by untrained workers. Hydrogen cyanide is lighter than air, accumulates at the top of enclosed spaces, and is rapidly dispersed by adequate ventilation
  4. Irritant gases (phosgene, chlorine, ammonia): These gases are heavier than air and accumulate at the bottom of enclosed spaces.
  5. Flammable liquid vapours (incl. LPG and Calor gas, propane and butane, and most solvents are vapours heavier than air): These tend to accumulate at the bottom of holds and storage lockers, and although not directly toxic displace breathable air and can asphyxiate crew who enter these areas.
  6. Freons: they are widely used as refrigerants. If a Freon is inhaled, it can cause severe cold injury (frostbite) of the respiratory tract. Heavy exposure can damage the heart, causing abnormal heart rhythm and sudden death.
  7. Hydrogen sulphide (“Rotten egg gas”, “Sewer gas”): it is produced in oil refining, and from decomposition of organic matter, especially manure. It is heavier than air and accumulates at the bottom of holds. Hydrogen sulphide is explosive and toxic. The smell is obvious at first, but the gas poisons the sense of smell so that after a few minutes the smell appears to have gone away even if concentrations are rising. Low concentrations irritate the nose, mouth and eyes. Higher concentrations cause poisoning identical to that of hydrogen cyanide.


Key precautious actions

  • Protective clothing (e.g. rubber or plastic gloves, aprons, boots) and breathing apparatus (compressed air systems, smoke helmets) for the handling of dangerous goods must be readily available on board ship and regularly inspected and cleaned or replaced.
  • Adequate washing and showering facilities should be available close to workplace.
  • An appropriate neutralizing substance should be applied to the site of a leakage or spillage: the area should be covered with sand or vermiculite, which should afterwards be removed to a safe place in a special container.
  • Holds and enclosed spaces in which toxic vapours and gases might accumulate should be properly ventilated and checked with a gas detector (not an explosive meter) before anyone is allowed to enter these places and also during cargo-handling operations.
  • Places used for the storage of dangerous goods should be decontaminated after use and/or before reuse.
  • Dangerous goods should not be stored or carried close to foodstuffs.


Recommended actions in case of exposure

In case of exposure to any of the gases mentioned above, normal pink skin colour (not blue) even in very severe cases - because oxygen is trapped in the blood - irritation of the eyes and nose, vomiting, weakness and seizures are among the most common symptoms. In such cases, the following actions are recommended:

  • Leave the danger zone at once and get into open space. While escaping, cover your nose and mouth with a wet cloth, if possible.
  • If you feel irritation in your eyes or throat, hold your breath and keep your eyes closed as much as possible while escaping.
  • If a crew member has been exposed to a toxic gas or vapour, put on rubber gloves and remove the crew member’s clothing and seal it in a plastic bag.
  • Have the crew member shower, washing all over with soap for 15 minutes, then rinse the eyes with water for 10 minutes.
  • Seek medical advice with a view to evacuation of the patient.
  • Give oxygen by a non-rebreathing mask at the highest possible flow rate.


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