🔍 Key Concepts

• Enclosed space entry hazards in cargo tanks • Behavior of petroleum vapors (heavier than air, toxicity, flammability) • Purpose and use of self-contained breathing apparatus (SCBA)

💭 Think About

• How does the fact that a tank is NOT certified "gas free" affect assumptions about oxygen level and toxic/flammable vapors? • Are there any conditions (location in the tank, weather, or short time exposure) that reliably make an uncertified tank safe to breathe in? • What is the safest general rule mariners are trained to follow before entering any space that may contain fuel vapors or lack oxygen?

✅ Before You Answer

• Verify what "gas free" actually means in tanker operations and enclosed space entry procedures • Consider whether petroleum vapors can stratify, move, or be stirred up, even if you start at the top or only stay a short time • Confirm standard practice: if air quality is not tested and certified safe, what respiratory protection is required for entry?