Vessel-Specific Hazards Flashcards
7 cards from real CMC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Vessel-Specific Hazards flashcards as text
When a marine chemist issues a 'Safe for Workers' certificate for a cargo tank, what condition regarding oxygen must be met?
Answer: Oxygen level must be between 19.5% and 22%
OSHA and NFPA 306 require oxygen levels between 19.5% and 22% for a space to be considered safe for workers without supplied air.
Which vessel space presents the greatest risk of hydrogen sulfide accumulation due to organic sludge decomposition?
Answer: Cargo tank after carrying crude oil
Crude oil cargo tanks accumulate sulfur-containing sludge that decomposes anaerobically to produce dangerous concentrations of H2S.
A void space adjacent to a fuel oil tank is being prepared for entry. What is the primary chemical hazard the marine chemist must evaluate beyond flammability?
Answer: Hydrocarbon vapor migration through tank boundaries
Hydrocarbon vapors can permeate through corroded or poorly sealed tank boundaries from adjacent fuel tanks, creating toxic and flammable atmospheres in void spaces.
During a ballast tank inspection on a chemical tanker, the marine chemist detects a slight sweet odor with readings of 1 ppm benzene. What is the appropriate action?
Answer: Issue a restricted entry certificate requiring air-supplied equipment
Even at 1 ppm benzene (the OSHA PEL-TWA), a restricted certificate requiring supplied-air equipment is appropriate given benzene's carcinogenicity and the need to maintain exposures as low as reasonably achievable.
What unique hazard do double-bottom tanks on bulk carriers present that single-bottom vessels do not?
Answer: Difficult ventilation geometry creating dead pockets of inert or toxic gas
Double-bottom tanks have complex internal framing with longitudinals and transverses that create stagnant pockets where toxic or oxygen-deficient atmospheres can persist despite general ventilation.
A marine chemist is called to certify a pump room on a product tanker. Benzene content in the previous cargo was less than 0.1%. Which standard governs the atmospheric testing requirements?
Answer: NFPA 306 in conjunction with applicable OSHA standards
NFPA 306 is the primary standard for controlling fire and explosion hazards on marine vessels in US ports, used in conjunction with applicable OSHA standards.
What is the significance of the 'Lower Explosive Limit' (LEL) reading of 10% on a combustible gas indicator when certifying a tank for hot work?
Answer: The space must be re-ventilated; hot work requires 0% LEL reading
NFPA 306 requires 0% LEL (gas-free condition) in any space where hot work is to be performed, and adjacent spaces must also meet this requirement.