Precautions Against Ignition, Static Electricity, Toxicity and Inert Gas Hazards
This domain examines the controls that stop cargo vapour from being ignited, the static precautions used during transfer, toxic exposure controls and inert gas practice. The exam expects specific control measures, not general safety slogans.
Ignition control
Eliminate naked flames, smoking, hot work, unapproved electrical equipment, engine exhaust sparks and portable electronics in hazardous zones. Use gas detection and permits before work. Intrinsically safe equipment is required in classified areas.
Static electricity
Bonding and grounding are not interchangeable: bonding equalises potential between equipment; grounding connects to the ship or earth. Avoid splash filling, start loading at reduced rate, allow relaxation time before sampling or dipping, and avoid synthetic clothing. Follow the ship/shore checklist.
Toxicity and inert gas
Hydrogen sulphide, benzene and carbon monoxide require gas detection, respiratory protection and exposure control. Inert gas, usually flue gas or nitrogen, keeps cargo tank oxygen at 8% or less by volume and maintains positive pressure. Inert gas is not breathable; tanks must be ventilated and tested before entry.
Worked example
After inerting, a cargo tank reads 9% oxygen. This is not acceptable. Continue inerting and recheck the oxygen and hydrocarbon readings, because the target is 8% or less by volume. Do not treat the tank as safe for entry: an inerted tank is a cargo-operation atmosphere, not a breathing atmosphere.
Traps that cost marks
Using smell as gas detection; confusing bonding with grounding; sampling immediately after loading without relaxation time; assuming inert gas makes a tank safe to enter; using a filter mask in an unknown atmosphere.