Tanks and holds in ships must be cleaned after their cargo has been
emptied. Regulations explain how ships’ holds and tanks can be cleaned,
where they can be cleaned and if there is waste left over, what must
happen to the waste.
Cleaning the tanks in oil tankers is dangerous as there is a chance of
an explosion. Fuel vapours in an empty tank are very explosive. Oil
tankers always clean their tanks at sea. The waste must be stored on
the ship and taken from the ship when it is in port.