arpadveress 
Interesting comments have been published back in 2011 – see link
It says:
Mobile phones are not intrinsically safe, meaning that they have the potential to produce a spark of such intensity that it could ignite a vapour air mix. In oil refinaries, although every effort is made to avoid having flammable vapour air mixtures present, accidents do happen, so it makes sense to keep potential sources of ignition away from these areas.
John Gresham, Liverpool, UK
The idea that mobile phones can detonate explosions is a complete fallacy. It has never happened in practice, and can’t even happen in theory. The signs are there because of the fear that a less than objective expert witness and a jury who ‘know’ that mobile phones are dangerous might lead to a multi-million dollar payout.
Tim, London UK
Mobile phones are radio transmitters – the radio frequency energy from a phone, although tiny, still has the potential to induce a spark in nearby metallic objects if the conditions are right, and ignite petroleum or other explosive vapours. That’s why it’s forbidden to use them at filling stations.
Ray Crabtree, Beccles, England
What this old chestnut AGAIN! The spark from a mobile signal is as near to a myth as makes no difference. However it is a theoretical possibility. Is the inconvenience of not being able to phone your bookie worth the zillion to one chance of causing another Buncefield? However most of us have sat at a computer and noticed our mobiles causing bip bipping through the speakers. Oil plants have many electronically controlled systems a stray signal could cause problems with all sorts of processes. So where life and limb is at risk; Hospitals, Petrol stations & aeroplanes etc. Your inane chat or even vital business call just aint worth the risk however small. Personally I would make speaking into mobile phone in any public place with a voice level above 50dBa a flogging offence!
G. Baker, S. Ockendon U.K
Interestingly, while research continues to show that mobile phones could cause an explosion where vapour is present (e.g. garage forecourt), wearing nylon clothing constitutes a much bigger danger as it is considerably more likely to produce a spark.
Ruairi, Dublin Ireland
While the risk of sparks is remote, it’s a continuance of the urban myth about mobiles causing petrol to explode at service stations.
Chris, Mt Victoria, NSW Australia
Oil and Gas facilities are subjected to Hazardous Area Classification, that state kind of explosion products that could be in the area, and the electrical protection to be use by the devices to be installed in that area. Some of them are intrinsically safe, some others are explosion proof… If you mobile fulfill any of these, you could use it… otherwise, you’re risking yourself and those around you.
Jorge Álvarez, Bogotá Colombia
According to ATEX Directive a mobile phone is an electronic device and it shall be certified – link
One more interesting article to subject – link
Keep up good work!
Arpad
