OCTCO/OCTF Exit Exam • Set 1 Question 25 of 30

What gas present in crude oil vapor is highly toxic with rotten egg smell at low levels?

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Direct Answer

Option C: Hydrogen Sulfide (H2S)

Hydrogen Sulfide (H2S) is a highly toxic, flammable gas naturally present in crude oils. It deadens the olfactory sense at low concentrations and poses severe health hazards, requiring continuous monitoring and strict personal protective equipment protocols per ISGOTT.

All Options

Methane

Nitrogen

Hydrogen Sulfide (H2S) (Correct Answer)

Carbon Dioxide

Detailed Explanation & Context

Relevant Framework: STCW 2010 Manila Amendments • DG Shipping E-Learning & Exit Exam Standards • Oil and Chemical Tanker Cargo Operations (OCTCO/OCTF).

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More Questions in OCTCO/OCTF Set 1

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Q1 What MARPOL Annex regulates prevention of oil pollution from tankers? Q2 What is the maximum oxygen content allowed in inert gas supplied to cargo tanks? Q3 What operation uses crude oil jets to clean sludges from tank walls during discharge? Q4 What condition is mandatory before starting Crude Oil Washing (COW)? Q5 What system monitors and controls oily water discharge overboard from slop tanks? Q6 What is the maximum instantaneous rate of oil discharge allowed outside Special Areas under MARPOL Annex I? Q7 What device stops hydrocarbon gas backflowing from cargo tanks into the machinery space? Q8 What instrument measures flammable vapor concentration as a percentage of LEL? Q9 What is Reid Vapor Pressure (RVP)? Q10 What device protects oil cargo tanks against overpressure or vacuum structural damage?