The Second Engineer is responsible for the machinery spaces and their pollution-prevention systems. Responsibilities include:

• Ensuring the oily water separator (OWS)/15 ppm system is operated correctly and that no oily water is discharged overboard except in compliance with MARPOL Annex I (i.e. within the discharge conditions - oil content <15 ppm, the ship en route, and the required distance from land; in special areas/coastal waters stricter rules apply, and in many coastal/port areas discharge is prohibited).
• Ensuring the bilge and sludge are retained and discharged to reception facilities in port, not overboard; maintaining the Oil Record Book (Part I) accurately.
• Ensuring no discharge of sewage (MARPOL IV) or garbage (MARPOL V) in coastal/port areas except as permitted; the sewage treatment plant and the garbage handling are operated correctly.
• Ensuring the ballast water is managed per the BWM Convention (no discharge of untreated ballast in coastal waters).
• Preventing any accidental discharge (e.g. from a leaking pipe, tank overflow, or a faulty valve) by good maintenance, correct operation, and the use of the SOPEP if a spill occurs.
• Ensuring the crew are trained and the pollution-prevention equipment is maintained and tested.

• The Second Engineer must ensure the engines and boilers are operated so that the exhaust is clean and does not emit excessive smoke (black smoke) in port, which is a form of air pollution and is often prohibited in port areas.
• This involves: correct fuel combustion (proper atomisation, air/fuel ratio, injector condition), avoiding overloading or rapid load changes that cause smoke, using compliant low-sulphur fuel in port/ECAs, and maintaining the engines/boilers.
• The ship must comply with the sulphur cap (0.50% global, 0.10% in ECAs) and the NOx requirements; the Second Engineer ensures the fuel changeover to low-sulphur fuel before entering an ECA/port and records it.
• The incinerator (if used) must be operated correctly and only for permitted waste, and not cause excessive smoke; the ship must not burn garbage that is prohibited.
• The Second Engineer ensures the exhaust gas cleaning (scrubber) if fitted operates correctly, and that the ship does not emit visible smoke or exceed the emission limits in port.

• The fire alarm (general alarm for fire) is distinguished by a specific signal: the general emergency alarm is seven short blasts followed by one prolonged blast (on the whistle/siren and the internal alarm), repeated. The fire alarm is a continuous ringing of the alarm bells or a distinct signal.
• The fire detection and alarm system (the fixed fire detection system) has its own audible and visual alarm at the control panel and throughout the ship, which is distinct from the general alarm and from other alarms (e.g. the machinery alarms, the CO2 discharge alarm, the watertight door alarm).
• The fire alarm is distinguished by its sound (a continuous or specific pattern) and by the visual indication (the zone/panel), and it is tested so that it is recognisable. The general emergency alarm (7 short + 1 long) is used for mustering for fire and other emergencies; the fire detection system's alarm is a separate, continuous alarm indicating a fire in a specific zone.
• The CO2 discharge alarm (a distinct warning) is also separate, warning personnel to evacuate before the gas is released.

• Every ship must be provided with an emergency source of electrical power (an emergency generator, or an emergency battery for smaller ships) capable of supplying the essential services in the event of failure of the main source of power.
• The emergency source of power must be located above the bulkhead deck, outside the machinery space, in a space that is fire-resisting and protected, and must be capable of starting automatically on loss of the main power (within 45 seconds) and supplying the emergency loads.
• The emergency power must supply: emergency lighting (in the machinery spaces, accommodation, escape routes, muster stations, lifeboat stations, and the navigation bridge), the navigation lights, the emergency fire pump, the watertight doors, the fire detection and alarm system, the communication systems (GMDSS), the steering gear (if required), and the emergency switchboard.
• The emergency generator must have its own fuel supply (a day tank) sufficient for the required period (e.g. 18 hours for cargo ships, 36 hours for passenger ships, or as required), and be tested periodically (e.g. monthly) to ensure it starts and supplies the emergency loads.
• The emergency switchboard must be arranged so that the emergency services are supplied automatically on failure of the main supply, and the changeover is tested.