This paper analyses the causes of fires on board merchant ships and fishing vessels. The study attempts to
identify the causes of fire occurrence on board ships and to determine their interrelations using the relations
diagram, also known as the interrelationship diagram or digraph. This diagram identifies relations not only
between causes and effects but also between two or more causes. Elements of the diagram, which have the
greatest number of directed connections from/to, are the starting points for further ship safety analysis. The
relations diagram is used as a basis for planning corrective measures and actions directly increasing shipping
safety at sea. Knowing the various causes of fire occurrence, it is possible to eliminate or to reduce their
number in the future by revising and drawing up relevant maritime transport regulations. This, in turn, can
enhance shipping safety.