The gas that is known as an inert gas is one that will not go undergo any chemical reactions when it is given a set of conditions. These gases will not react with a wide range of substances. It is is for this reason why inert gases are used and this is so as to avoid any reactions that may take place between different chemicals. The usual type of reaction that can happen between chemicals which need to be avoided include oxidization, as well as hydrolysis and these reactions will happen when there is a combination of moisture and oxygen within the air.
Inert gases will often be used on ships and in the marine industry and this will often be the case on crude oil carriers, you can read more http://www.giaearth.com/products/inert-gas-system. In this situation the inert gas will be used in a flue gas system or in a inert gas generator. It is used to prevent the atmosphere that will be found in the bunkers and the cargo tanks from coming in a range that may be explosive. It does this by keeping the oxygen content within the 5% range and below so that the atmosphere does not become dangerous. Once this has happened the hydrocarbon and the mixture of gas will not be too rich and therefore will not be able to ignite and explode.
Inert gas is also used used in the marine industry for underwater diving and is created from a mixture so as to allow the breathing to be carried out in a way that is safe and so that there is not any chemical based active components that may take affect and have a negative affect on those that are diving. When inert gas is used on the commercial diving industry, the inert gas which is used the most is that of helium.