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Q: When rusting of a ship’s steelworks occurs, which ONE of the following is the main effect on the air inside a ballast tank or cargo tank?
A: The oxygen content of the air decreases.

Q: Which of the following toxicity threshold limit exposure terms would normally have the lowest numerical value?
A: TLV-C

Q: Which term is used for the property of a substance that has a long-term harmful effect on a living organism as a result of repeated or long-term exposure to it, even at low concentrations?
A: Chronic toxicity

Q: What is the time period that is normally used when stating threshold limit values for the Time Weighted Average for exposure, TLV-TWA, for toxic gases?
A: 8 hours.

Q: The oxygen content in an enclosed space falls below 21% during entry by personnel. What action should be taken?
A: Stop working and leave the space immediately.

Q: What is the time period used when stating threshold limit values for the Short-Term Exposure Limit, TLV-STEL, for toxic gases?
A: 15 minutes.

Q: What is the most common source of hydrogen sulphide gas in enclosed spaces onboard a ship?
A: Sour crude or petroleum products from sour crude tanks.

Q: The combustion control of an independent inert gas generator, supplying inert gas to a cargo tank system, is incorrectly set, giving incomplete combustion. What is the likely effect of this?
A: Increased level of carbon monoxide in the inert gas.

Q: Which ONE of the following options, best completes the following statement? Onboard a ship, an enclosed space is any space which…
A: has limited ventilation or could contain toxic or flammable vapours.

Q: What is the most likely reason for the presence of high levels of oxides of Nitrogen and Sulphur (NOx and SOx) in the atmosphere of a cargo tank on an oil tanker?
A: Inert gas from the combustion of fuel oil has been used to inert the tank.

Q: What is the normally accepted value for the upper explosive limit (UEL) for hydrocarbon gas in a cargo tank?
A: 8% by volume.

Q: What is the purpose of gas freeing a cargo tank?
A: To replace the contents with fresh air.

Q: What is the normally accepted value for the maximum oxygen content in an inerted cargo tank?
A: 8% by volume.

Q: What is the effect on the oxygen content of the atmosphere of an enclosed space if hydrocarbon gases are present?
A: Oxygen content is reduced.

Q: What is the normally accepted value for the lower explosive limit (LEL), for hydrocarbon gas in a cargo tank?
A: 1% by volume.

Q: What are the two main reasons for measuring the oxygen content of an enclosed space onboard a ship?
A: To check if the oxygen content is low enough to avoid flammable mixtures. To ensure the oxygen content is sufficient to allow safe entry.

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