The ISM Code requires the Company to identify the ship's critical equipment and systems - those whose sudden loss could endanger the ship, crew or the environment. The factors considered include:

• The consequence of failure: equipment whose failure could cause a serious accident, loss of life, pollution, or loss of the ship (e.g. steering gear, main engine, generators, emergency generator, fire pumps, OWS, ballast/cargo control, navigation equipment).
• The safety and environmental impact: systems that protect the ship and the environment (firefighting, lifesaving, pollution-prevention, watertight integrity).
• The operational criticality: equipment essential for the ship's safe operation and propulsion (main engine, steering, power generation, propulsion control).
• The redundancy: whether there is a backup (e.g. a standby generator, a second steering system); equipment without redundancy is more critical.
• The maintenance requirements: equipment that requires regular testing and maintenance to remain reliable.
• The regulatory requirements: equipment required by the conventions (SOLAS, MARPOL) and the class/flag requirements.
• The risk assessment: the likelihood and consequence of failure, and the risk to the ship, crew and environment.

Based on these factors, the Company identifies the critical equipment, specifies the tests and checks to be carried out at stated intervals, and determines the minimum spares and stores required.

Identifying critical equipment is important because:

• It ensures that the equipment whose failure could endanger the ship, crew or environment is maintained, tested and monitored to a high standard, reducing the risk of failure.
• It allows the Company to specify the required tests, checks and maintenance, and to ensure the minimum spares are carried, so the equipment is ready when needed.
• It focuses the maintenance and inspection resources on the most important equipment, improving safety and reliability.
• It supports the risk-assessment and emergency-preparedness approach of the ISM Code, and ensures that the crew are aware of the critical systems and their operation.
• It helps prevent accidents, pollution and loss of the ship, and demonstrates compliance with the ISM Code.
• It enables the Company to plan for contingencies (e.g. the availability of spares, technical support) and to respond effectively to a failure.

Overall, identifying critical equipment is fundamental to the safe operation of the ship and the effective implementation of the SMS.