Fumigation. When the vessel has rats or other vermin on board, and also infestation from cargo, these undesirable elements must be eliminated. This is done by fumigation. Some fumigation agents may be toxic for humans.
Under International Health Regulations, all ocean vessels must be in possession of a certificate of deratisation, which is valid for a maximum of six months. The validity can be extended by one month if the vessel can be inspected or fumigated at the next port. If the vessel is free from rats or if the number is limited, it may not be necessary to fumigate. In that case a “Deratisation Exemption Certificate” will be issued by the competent authorities and is also valid for six months.
Apart from the delay to the vessel, fumigation is an expensive measure so that it is imperative to take all necessary precautions. Fumigation may also be necessary to minimise infestation when certain cargoes are carried, rice or other grains.