Agree with all the above (particularly the basic
facts presented by people such as QNH1013 / Maxflyer and others). As with all things, a modicum of common sense, correctly applied, goes a long way.
eg. When I was flying a PA28 at night out of Bournemouth and wanted to refuel at the end of the sortie, the E$$o (don't want any advertising, do we, BRL
) bowser would turn up and need to see inside the tanks to refuel to the tabs. As he'd quite often not have a free hand, he'd ask me to shine a torch into the tank. He'd usually offer me his intrinsically safe one, but on occasions, that may not have been readily available, so I would use my Maglite (sorry, unintentional advertising, BRL!
) to illuminate it. Common sense dictated, however, that it would be turned on / off at a safe distance from the filler / nozzle to eliminate possible risks from arcing switch contacts.
So, I would say that the risks associated with mobile phones are predominantly due to RF field energy and switching on / off. If you're a few metres away from any ready source of petrol vapour, then there's no issue. With Jet-A1 / AVTUR / Diesel, I believe that the vapour pressure is so much lower that I would pretty well say the risk is so low as to be below negligible.
HOWEVER, Health and Safety is all about minimising risks, so I'm sure they will try to reduce a 'below negligible risk' to zero!!
