When I used to work in the mines the conditions in many ways resembled those on Oil rigs, especially underground as the atmosphere in most places could (in the wrong circumstances) become explosive, as a result smoking was not only forbidden but under the Mines and Quarries Act actually a criminal offence, also all electrical equipment had to be rigourously tested and certified for use in gaseous conditions and I imagine a similar system covers oil rigs, Especially since the disaster involving the Piper Alpha in which I lost several close friends , as the oil companies liked coal board trained craftsmen as they were used to working in potentially explosive atmospheres