Over the Christmas period I watched a great show called "Brainiacs" on Sky One. The aim of the show is one which sent shudders through my spine "to put the fun into science" - something which normally fails badly but this really worked and grabbed my attention (although it has to be said they erred on the side of fun rather than science).

Fire extinguisher propelled wheelchairs and human guinea pigs testing the effects of an electric fence were both funny and interesting (and raised some interesting questions about what I thought you could get away with on television - I'd love to see the legal waiver the participants had to sign), but what really caught my eye was the test of the reasoning behind not using mobile phones in petrol stations.

This is something I've pondered for a while as I fill up my motor with petrol. Signs everywhere warning me not use my mobile phone on the forecourt, but why? Can they really spark an explosion and if so why don't you every read about this happening in the newspapers? Even the normally informative snopes, despite deciding overall that it is false, is fairly inconclusive on the subject if you read through the whole report.

Anyway the televised experiment, while hardly compehensive, provided some entertaining evidence that the whole thing is rubbish. Take one caravan (always a good start - the potential destruction of a bloody caravan - speaking as an ex-patriot Cornishman caravans are the scourge of the roadways) and fill it with petrol fumes. Add half a dozen mobile phones, retire to a safe distance, and dial.

Unsurprisingly no-one answered the phone, and more satisfyingly no explosion resulted. Urban fact becomes urban myth. Hurrah! Although the scientist in me thinks that just the one test was perhaps not enough. Not good televsion to sit there repeating it though I guess. Of course the only real problem at this point was that the bloody caravan was still in one piece. What else could they test that would lead to it's destruction? Well there's always smoking but that might have been asking too much of the volunteers on the show.

Step forward the nylon shell suit. Yes - bad fashion on the forecourt is dangerous. A cable was trailed into the caravan and another trusty volunteer in nylon clothes jumped around alot before discharging the resulting static onto the bare copper end of the wire. One visible spark later and the caravan was a fireball.

Hurray! We can use our mobiles safely in the petrol station, people wearing shell suits will explode, and the world contains one less caravan. Science is fun. If you see this show is going to be repeated I highly recommend tuning in.

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You're right about that experiment being inconclusive, for the obvious reason that they only tested what happens if the phone rings -- they didn't test what happens when you press a button or two on a mobile. But I don't happen to believe that will cause a spark capable of ignition either. Personally I think it's much more likely to be a scare tactic in place of the reason "If you're using the phone you're not really concentrating on the task in hand, and will probably end up splashing petrol all over yourself". ;)

That makes a lot of sense. Is the conclusion then that if you must use your mobile phone in a petrol station make sure you have a diesel car? Having got diesel on my hands before (the stuff is foul) there's no way you would splash it around. Although having said that there would be no spark risk with diesel would there?

I'm not entirely sure about diesel; <a href="http://en.wikipedia.org/wiki/Flash_point">wikipedia says</a> diesel's flash point is much higher than petrol's [above 45 degrees centigrade], but I don't know how that translates into risk of a random spark causing ignition. I think we all agree: more experiments are required!

Are you volunteering? If so this has to be a <a href="http://fuddland.org.uk/moblog/">moblog moment</a>. Might be your last though...

I did once have lighter fluid poured into my cupped hands and set alight, but that was at school. Not part of a radical science syllabus -- just a really, really stupid dare. Thank God I was too cool to wear shellsuits! [Well, I'm not admitting to owning one anyway. ;) ]

I didn't know you were from Cornwall!

Well to be strictly honest I left when I was 12 which was *ahem* a few years ago now. I still miss it every now and again though and it kind of still feels like home even though I've since moved around the country a lot.

Strangely I've only been back once in all this time, and even then not to the places I lived. The thing I most miss now is having a Cornish accent - I really like West Country voices and if listening to my answering machine is anything to go by I sound very Londonish now - it's fairly hard to judge your own speech though.

Just for the record, while I'm on the subject, the variety of places I've lived include:
<ul>
<li>St.Blazy Gate, Cornwall
<li>St.Austell, Cornwall
<li>Newbury, Berkshire
<li>Stoke-on-Trent, Staffordshire
<li>Bristol
<li
>Farnham,
Surrey
<li>Bordon, Hampshire
<li>Mytchett, Surrey
<li>Ash, Hampshire
<li>Ash Vale, Surrey
</ul>
Quite a lot. but rather frustratingly all in the UK.

i know my friend mas had the same phone for 5 years now, and his battery disconnects all the time, and i can guarantee you there is some definate sparking there... maybe something weird like that happened once and they just want to be sure it never does again... i always obey stupid signs like that because if it doesn't make any sense then the only way they could have figured it's a bad idea is if it happened...

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