🔍 Key Concepts

• Crude oil washing safety procedures (oxygen limits and where measurements must be taken) • How oxygen concentration can vary with height inside a tank • Why regulations require measuring at the most dangerous (highest O₂) location rather than the easiest location

💭 Think About

• Think about where in a cargo tank oxygen is most likely to be higher when there is oil and inert gas present—near the liquid surface, higher up, or in the vent line? • If you want to be sure the ENTIRE tank is safe for crude oil washing, should you measure where it is most inert, or where oxygen is likely to be greatest? • Which option describes a specific, repeatable location inside the tank that best represents the worst‑case oxygen concentration for safety checks?

✅ Before You Answer

• Verify which options are inside the tank volume versus in associated piping or outside spaces • Check which position would likely show the highest oxygen content if air leaks in or mixing is imperfect • Confirm that the chosen position is a standardized, regulatory reference point used in crude oil washing procedures (rather than just a convenient spot)