Ships have lots of gas detection on board. Most areas below deck are a confined space of one sort or another. The ship will therefore have a multi-channel portable on board. It will also probably have a number of personal flammable gas or oxygen monitors. With this they will need all the suitable calibration equipment for the devices so they can carry out calibrations whilst at sea.
Large ships that carry flammable liquids, like oil tankers, will generally have a need for fixed detection equipment in the pump room. Senko have a system based around SI-100IM which could be used for this.