Question 64 ONC04 - Mate of LT 500-1600 GRT

The Correct Answer is A. **Explanation for A (An inert gas system):** An Inert Gas System (IGS) is specifically designed and mandated by both Coast Guard and international (SOLAS/MARPOL) regulations for use on large tank vessels. Its primary function is safety. It works by introducing an oxygen-deficient gas (inert gas, typically produced by scrubbing boiler flue gas or using a dedicated generator) into the cargo tanks, which reduces the oxygen concentration to below the level necessary to support combustion (typically below 8% by volume). This process achieves both: 1. **Fire Prevention:** By maintaining an atmosphere too lean to burn. 2. **Simultaneous Inerting of Cargo Tanks:** By creating the non-combustible atmosphere within the tank free space. **Explanation why other options are incorrect:** * **B) The fire main system:** The fire main delivers water for firefighting (cooling and smothering) but does not provide inert gas to prevent combustion or simultaneously inert the cargo tank atmosphere. Introducing water into the tank atmosphere would not inherently lower the oxygen content effectively for inerting. * **C) A fixed water spray system:** While effective for cooling external surfaces or suppressing deck fires, a water spray system is an active firefighting system, not a system for inerting the tank atmosphere or for continuous fire prevention *within* the cargo tanks through oxygen reduction. * **D) The deck foam system:** The deck foam system is a firefighting system designed to rapidly blanket the cargo deck (or extinguish spill fires on the deck) by creating a layer of foam that suppresses vapor release and smothers the fire. It is used for firefighting, not for inerting the internal atmosphere of the cargo tanks for fire prevention.