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In my spare time, I am a volunteer for the fire brigade. Yesterday I was attending a lessons about preventing fires, and we saw a movie about a lady fueling her car while receiving a call. And "boom"! The fuel, and later the car, exploded because her cell phone got a call. The teacher told us it was because her cell phone gave an electrical signal (a kind of spark) and by so light up the whole place.

Since I tend to carry my iPhone 4S in my pockets all the time, I'm concerned about the risk of entering a building filled with some gas. If I get a call when I'm in such a building, I'm afraid I won't be around to answer the call anymore. :)

So, the teacher told us there are special cell phones which are explosion proof. These phones don't generate a spark or detectable electric signal of any kind when receiving a call.

Is the iPhone 4S such a cell phone? In other words, is it safe to carry an iPhone 4S when entering a building filled with gas?

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I'd like to have some more background on the first paragraph. I can't really imagine how this is supposed to work. Also, I thought that the term 'explosion proof' mobile phone refers to a phone that can withstand explosions. –  gentmatt Jan 20 '12 at 9:46
    
I think this scenario (gas station explosion started by a phone call) is some urban legend. –  Martin Jan 20 '12 at 9:52
    
I edited the first paragraph. 'Explosion proof' might be a bad translation. I mean, is the iPhone 4S an igniter for things like gas or fuel... –  Michiel Jan 20 '12 at 9:53
    
@Martin, it might be. But yesterday we saw a movie and testimony from a fireman. So, I think it was real :) –  Michiel Jan 20 '12 at 9:54
    
@Michiel Maybe you can add this video to your question as a 'proof of concept'. :) youtube.com/watch?v=nyYCu2K-NYQ –  gentmatt Jan 20 '12 at 9:56

2 Answers 2

up vote 21 down vote accepted

To cut it short: This assumption is false.

Cellphone are not able to cause high voltage sparks required to light gas. Probably only if short-circuited.

Mythbusters investigated this problem. Their answer was that such accidents were caused by static charge on the person, not by cellphones.

This is important to notice as "Petrol has a low electrical conductivity. This can cause a charge of static electricity to build up as it flows through a pipe."[1] When both the petrol and the person are charged, there is a potential spark discharge in the gap between.

Edit:

  • A BBC news article mentioned that research has been conducted on the matter by Dr Adam Burgess of the University of Kent. The publication is called: ‘Phantom Risk: The Curious Case of Mobile Phones, Fire and Body Static,’ Health, Risk and Society 9 (1) 2007 ISSN: 1369-8575 and available here.

  • [1] The Australian Transport Safety Bureau has published a paper called 'Static Fires at Petrol Stations' which is publicly available for download.

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Ok, if Mythbusters investigated this issue, I'm tending to believe it. But what about the testimony about lighting up a house filled with gas by receiving a cellphone call? –  Michiel Jan 20 '12 at 10:17
    
The only situation where I can think of sparks in mobile phones is this: Old mobile phones which have an extended antenna. The thin end of an antenna is where the magnetic field is the strongest. This is where a spark could come from. I believe that an honest investigation requires much more background information. You need to know what mobile phone was used an how it was built inside. A general answer should not be possible. –  gentmatt Jan 20 '12 at 10:24
    
A high voltage and low current static discharge are the ones that ignite flammable gases. A visit to wikipedia or a science museum will cover the basics - furry cloth rubbed on glass or acrylic causes triboelectric charging and it's entirely possible to build up a good charge on any cell phone as you take it out of a pocket. It's not so much the electricity from the battery, but the charge built up on the phone or the person that has potential to cause ignition. Any object - even an iPhone with a dead battery could trigger this. –  bmike Jan 20 '12 at 18:59
    
Yet, it's unlikely that triboelectric charge on the phone in your pocket is the cause. As soon as you get hold of the phone with your bare hand, potential net charge distributes over your body causing a large drop in electric potential difference. The tribolectric charging would require more effort I assume - e.g. rubbing in your seat like the bear baloo. In the reported cases that I've seen on video the people were not wearing gloves. –  gentmatt Jan 20 '12 at 19:21

The iPhone is not explosion proof.

There have been a number of reports of iPhone exploding, one such report details how an iPhone exploded on an Australian airline without any reason.

So hopefully that helps you out a bit.

Although I cannot confirm that this is due to exposure to gasses, they can explode.

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Ok, thanks for your answer. But I'm not interested in a exploding iPhone, more in the question whether or not an iPhone is giving some electrical spark when receiving a signal... –  Michiel Jan 20 '12 at 9:37
    
Why should the iPhone (or any other mobile phone) give some electrical spark when it receives a call? –  Martin Jan 20 '12 at 9:51
    
I don't know, maybe because of the electrical transmission? –  Michiel Jan 20 '12 at 10:13
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@Michiel There are no sparks. Your phone isn't filled with Tesla coils. I'm sure they told you guys about the 3 components of a fire in your course: fuel, oxygen, and an ignition source. The only way the iPhone could provide an ignition is if its battery cracked and the contents discharged. During normal operation, there are no sparks or other volatile "electrical transmissions." It's a shame your course chooses to spread falsities and prey on ignorance rather than provide clear and reliable information to help you guys assess a situation. –  cksum Jan 20 '12 at 17:08
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Catching on fire or deforming isn't exploding. All lithium polymer batteries can emit gases when overcharged or damaged leading to fire. I've never seen a credible report that the batteries in an iPhone hasn't vented prior to the theoretical point of explosion. A bad battery will almost always self-ignite and consume or vent due to structural failure far before a sufficient amount of explosive gases can form. I've seen plenty of deformed cells, but none that punctured other than someone poking at them when distended. (which is a REALLY BAD IDEA BTW) –  bmike Jan 20 '12 at 19:04

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