SUNBEAM is moored stern-to a quay overnight with the engine running to charge the batteries. Two crew below decks start to get headaches and feel drowsy and a bit sick. What should be suspected straight away?

A. Carbon monoxide (CO) poisoning from engine exhaust fumes — CO is invisible and has no smell, so headache, drowsiness, and feeling sick with no other obvious cause, especially with an engine running nearby, should always raise this possibility immediately

B. Seasickness, even though the boat is moored still in harbour and not moving

C. A normal reaction to being in a small cabin and not worth investigating

D. Simple tiredness from a long day — nothing further needs to be considered

A. Wait a few minutes to see if the headache passes on its own before doing anything

B. Turn off the engine immediately and get everyone out into fresh air on deck straight away — stopping the source and getting clean air to the casualties matters more than anything else in the first moments

C. Move the affected crew to a different part of the cabin, away from fresh air, to rest quietly

D. Open a small hatch slightly but keep the engine running, since it is needed for the battery charge

A. Assume that anyone who can still walk around is completely unaffected

B. Only check the two people who already complained — everyone else is automatically fine

C. There is no need to check anyone else since the engine is now off

D. Check every single person aboard for any symptoms, even mild ones, since CO can affect people differently and some may not yet have noticed anything; do a headcount to be sure no one is still below decks, especially anyone who might have been asleep