When crude oil or other refinery products are transported, there is always the hazard of explosive gas mixtures being formed in the cargo tanks of oil tankers. To prevent air entering the tank and the formation of explosive vapors, cargo tanks of ships are blanketed with inert gases such as nitrogen.
In the shipping industry it is common to blanket tanks with inert gas during loading, purging, crude oil washing and to top-up the load with inert gas during the voyage.
To prevent oxygen exceeding the safe level it has to be measured during all of these situations.
In some cases, the vessel will have its own gas generators where the quality of the generated nitrogen has to be determined using oxygen measurement.
Industry Links
Methanol.org
chemicaltankerguide.com
airproducts.com
International Chamber of Shipping
Health and Safety Executive