CMC Vessel-Specific Hazards 2

Question 1

When a marine chemist issues a 'Safe for Workers' certificate for a cargo tank, what condition regarding oxygen must be met?

Accepted Answer

Oxygen level must be between 19.5% and 22%

Answer

OSHA and NFPA 306 require oxygen levels between 19.5% and 22% for a space to be considered safe for workers without supplied air.

Question 2

Which vessel space presents the greatest risk of hydrogen sulfide accumulation due to organic sludge decomposition?

Accepted Answer

Cargo tank after carrying crude oil

Answer

Crude oil cargo tanks accumulate sulfur-containing sludge that decomposes anaerobically to produce dangerous concentrations of H2S.

Question 3

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?

Accepted Answer

Hydrocarbon vapor migration through tank boundaries

Answer

Hydrocarbon vapors can permeate through corroded or poorly sealed tank boundaries from adjacent fuel tanks, creating toxic and flammable atmospheres in void spaces.

Question 4

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?

Accepted Answer

Issue a restricted entry certificate requiring air-supplied equipment

Answer

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.

Question 5

What unique hazard do double-bottom tanks on bulk carriers present that single-bottom vessels do not?

Accepted Answer

Difficult ventilation geometry creating dead pockets of inert or toxic gas

Answer

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.

(CMC) Certified Marine Chemist Practice Test

(CMC) Certified Marine Chemist Practice Test

CMC Vessel-Specific Hazards 2