This paper discusses the possibilities and risks of hydrogen sulfide (H2S) poisoning on merchant navy ships. In practice, we often hear about the dangers to which workers on these types of ships are exposed, the equipment and certain training that every seafarer must undergo is crucial in reducing the number of such accidents. Toxic gases can enter the body very easily, usually through the respiratory system, but it is also possible poisoning by contact with the skin if the gas is liquefied or in contact with the mucous membrane of the eye. The gas we often come across on merchant ships is precisely hydrogen sulfide. If a person is exposed to an excessive amount of this gas, it becomes extremely harmful and can lead to fatal consequences and thus even death. The gas carries with it the smell of rotten eggs, so it is possible to spot and repair it in time, but we must not ignore it in any way. Accidents and poisonings with H2S most often occur on the ships of the merchant navy, ie in the closed spaces of these ships. The biggest problem occurs when cleaning enclosed spaces in which a certain cargo was transported, which is expected to contain H2S. The paper describes how to identify hydrogen sulfide, the places and procedures to be followed when handling this gas as well as the procedures to know if contamination with H2S occurs.