🔍 Key Concepts

• Inert gas systems (IGS) requirements for tankers carrying flammable cargoes • The purpose of maintaining a non-flammable atmosphere in cargo tanks and associated piping • Typical regulatory limit for oxygen percentage in inerted spaces to ensure vapors remain below flammable range

💭 Think About

• Ask yourself: At what oxygen level is a hydrocarbon/air mixture generally considered non-flammable in tanker practice? • Consider: Is the allowable limit set just below the flammability threshold, or with a safety margin beneath that? • Think: Which of these percentages is commonly quoted in tanker operations manuals and IGS alarms for too-high oxygen content?

✅ Before You Answer

• Verify the typical oxygen alarm set-point used in inert gas systems on tankers for cargo tanks • Check what SOLAS/IGS guidance gives as the maximum oxygen content for an atmosphere to be considered safely inerted • Eliminate any option that is clearly within the normal flammable range for hydrocarbon vapors in air