Information regarding the safe carriage of hazardous substances as cargo can be obtained from several key international codes and conventions. The primary source is SOLAS (Safety of Life at Sea) Chapter VII, which outlines the regulations for carrying dangerous goods. This chapter is further supplemented by specific codes tailored to the type of cargo and its form.

• Part A: Deals with dangerous goods in packaged form and refers to the International Maritime Dangerous Goods (IMDG) Code.
• Part A-1: Covers dangerous goods in solid form in bulk, and the relevant code is the Code of Safe Practice for Solid Bulk Cargoes (BC Code).
• Part B: Pertains to the construction and equipment of ships carrying dangerous liquid chemicals in bulk, governed by the International Bulk Chemical (IBC) Code.
• Part C: Relates to the construction and equipment of ships carrying liquefied gases in bulk, and the applicable code is the International Gas Carrier (IGC) Code.
• Part D: Outlines special requirements for the carriage of wastes, specifically referring to the International Code for the Safe Carriage of Packaged Irradiated Nuclear Fuel, Plutonium and High-Level Radioactive Wastes on Board Ships (INF Code).

Phosphoric acid (H3​PO4​) is a hazardous substance that requires specific handling and safety precautions during transport.

(i) Storage and Transport

Phosphoric acid should be stored in a cool, well-ventilated area away from heat, fire, and incompatible materials like combustible substances, strong bases, and metals. Large storage tanks must be bundled and electrically grounded.

The substance is typically transported in high-density polyethylene (HDPE) jerrycans (50 kg), HDPE barrels (170 kg), or in dedicated tankers or ISO containers. To prevent corrosive reactions, it's crucial to avoid using glass or unprotected steel containers.

(ii) Hazardous Properties

While not combustible itself, phosphoric acid poses several hazards. It can release toxic substances like fluorine compounds and hydrogen fluoride if the wet-process acid is heated. Thermal decomposition can also release toxic phosphorus oxide and hydrogen gas, which is flammable and can lead to an explosion. Under extreme heat, it can decompose into phosphorus pentoxide, a toxic, strongly oxidizing, and corrosive substance.

Phosphoric acid is considered moderately toxic. Physical contact with the liquid may cause irritation, burns, or mild corrosive action on the skin. Prolonged or repeated contact can lead to dermatitis.

(iii) Firefighting and Suppression Techniques

Phosphoric acid does not burn, so no special firefighting techniques are required to extinguish the substance itself. In the event of a fire involving containers or structures exposed to the acid, a water spray should be used to cool them. Standard cargo ship firefighting and suppression measures are sufficient for dealing with fires in the vicinity of the cargo.

(iv) Medical Effects and Treatment

Contact with phosphoric acid can have various medical effects, requiring immediate first aid. Safety showers and eye-washing facilities should always be available where contact might occur.

• Skin Contact: Causes redness and burns, which may not be immediately apparent.
  • First Aid: Wash the affected area thoroughly with large amounts of water.
• Eye Contact: Splashes cause irritation and burns.
  • First Aid: Flush the eyes with a large amount of water.
• Inhalation: Mists can irritate the respiratory tract, although entry into the human system via inhalation is rare. If exposure exceeds recommended limits, use a gas mask or self-contained breathing apparatus (SCBA).
• Ingestion: Can cause burns in the mouth and throat, as well as gastrointestinal irritation, pain, difficulty swallowing, thirst, nausea, vomiting, and diarrhea. Severe cases can lead to collapse and death.
  • First Aid: The victim should drink a large amount of water to dilute the acid.

  In all serious cases, immediate qualified medical help is essential. Workers handling the substance should wear appropriate personal protective equipment (PPE), including PVC gloves, boots, a resistant apron, protective clothing, and chemical safety goggles or a full face shield.