🔍 Key Concepts

• Inert gas system purpose on tankers (why we use it for cargo tanks) • The minimum oxygen concentration needed to support combustion of hydrocarbon vapors • Relevant standards in SOLAS for inert gas systems on tankers

💭 Think About

• Think about what oxygen level is generally considered too low to support burning of most hydrocarbon cargo vapors. • Compare that typical ‘safe’ oxygen percentage with each of the choices given; which one clearly falls below the combustion-support threshold? • Ask yourself whether the standard is set with a safety margin below the point where ignition is possible, or right at the limit.

✅ Before You Answer

• Verify in SOLAS requirements for inert gas systems the maximum allowable oxygen content delivered to cargo tanks. • Check which answer choices are clearly above normal atmospheric oxygen (about 21%) and which are significantly below it. • Confirm that the correct choice reflects a value that is low enough to reliably prevent combustion of most petroleum vapors, with a margin of safety.