Your observations would indicate that it might not happen very often (and indeed it does not) but anything to do with RF, and complex, changing geometry, has so many possible scenarios that wheer the transmitter power is at the level of 1.5 watts, there will be exact configurations when disaster will occur. It is quite a low power level, but well above what is needed for ignition. In some conditions, a fair proportion of the power may well end up where it is least wanted. A few milliwatts in the wrong place is all it takes.
If you are so sure of that, will you please tell me the actual power of the phone, and the power produced by the static. I happen to know the answers, but do you? Will you tell us the energy dissipated in a 10 millisecond interval by each, for example?
And because something does not happen 99 times out of 100, it does not follow that it can't happen, especially when theory and tests which date back to way before mobiles were invented show that the relevant RF power level does present an ingition hazard.
As for the effcets on aircraft, I am by profession an avionics designer (with a huge amount of safety, RF/EMC, even software, thrown in for good measure. I also have an honours degree in physics. I am well placed to know that all but the very latest aircraft have vulnerabilities in their systems because when they were designed, the threat presented by mobile phones on board, within the fusleage, did not exist. There have been a number of incidents involving uncommanded manoeuvers, and malfuntion of various systems, strangely in every case, the problems went away when the phone concerned was switched off, and returned when it was swithed on again. If that does not constitute proof, I do not know what does, and of course any uncommanded manoeuver could easily turn into a disaster.
For that reason, people who do not switch off their phones while on board aircraft should automatically receieve severe prison sentences, and fortunately at least one UK court agreed, I think the guy got 2 years.
The spark happens when an antenna, typically the pump nozzle, receives RF energy and converts it into voltage and current, which then may cause a spark between the antenna and another bit of metal, also technically an antenna but it will function more like ground in this instance, the vehicle body. The sparks will be smallish and will only happen as the nozzle makes and breaks contact with the vehicle. To a casual observer, when a fire happens it will look the same as one caused by static. Some of the fires have happened in wet weather when the possibility of static electricity is extremely remote, RF sparking of the sort that matters here is not affected very much by the weather, but mostly by the nature of the two surfaces that are in interemittent contact. It is affected very much indeed by the field strength, below a certain level there is no significant risk.
However, as regards the battery theory, if you directly short a charged mobile battery, some types will catch fire or explode after a short while, within themselves, and yes you can produce sparks sufficient to ignite petrol from a small battery, again by means of an intermittent connection, DC is just as effective as RF.
Yes, that is precisely your score, because you have no comprehension of the issues involved. It is people like you, asserting their opinion that danger is in fact safety, from a position of wilful ignorance, that are dangerous. Come to think of it, that is exactly what politicians do, so I guess you must be one. I simply switch off my phone and endanger no-one.
My posts are always controversial, unless I am condemning the Monopolist. I am usually on safe ground there!
Your experiment is interesting, but does not tell the whole story, you really need to try to make sparks with two bits of metal (one maybe resonant) lightly brushing against one another. You will need good equipment to see the sparks, but if you can devise such an experiment, I think you will be convinced.
You don't need anything like 90 volts.
AFAIK, "intrinsically safe" electrical circuits are limited to a few volta and a few milliamps. If you look up those standards and see how low it does need to be to avoid all risk, and then do some measurements of actual RF voltages with the appropriate instrument, I think you will be convinced.
I have in the past done a fair bit of EMC testing, and when you are appling an external field it is quite amazing what voltages can appear if anything resonates. It does not need more than a few volts to get sustained (but minor) arcing if the conditions are right. Of course where petrol is concerned, a minor arc is all that might be needed.
But, I hope you wil be able to see all this by experiment, it should be fun.
Yes, quite amazing what unthinking people will do, some of them will manage to make almost any situation dangerous eventually.
In the UK we don't have latching pump valves any more, at least I have not seen them lately, maybe for this reason. When we did have them, they were regulated by law such that they had to reliably shut off if the back pressure in the nozzle became too great, one of my old cars had a long and narrow neck, and the lever had to be held dowm manualy or it would trip.
I think you have convincingly shown that cell phones are dangerous in filling stations, not just because of the RF hazard!
Your assumptions are entirely wrong, and I suggest that you read up on basic electrical theory.
The "Q" factor of a resonant circuit used to be called the "magnification factor" becaus ethat is exactly what it does. It does not produce energy out of nowhere, but your assumptions about the possible magnitude of theinduced voltages are well off the mark, as you would know if you had ever done any EMC testing, for example.
Also, how vapours ignite is a complex issue, but often a static spark will not do the job (not something to rely on of course) because it represents a fixed amount of energy dissipated in a few nanoseconds. If the pump nozzle is picking up some RF voltage, and is brushing against the neck of the tank, there can be multiple sparks over a short period of time, the actual energy input can be higher, and so the probability of ignition can be higher.
Read your sig, and understand the inverse square law!
Consider where the signs are in relation to the pumps, and where a mobile might be.....
It is ironic as you say, because it sends the wrong message to the public, who do not understand the issue, and imagine it must be safe to use their mobile 100 times closer to the tank they are filling.
Yes and no.... It is not the direct energy of the RF field, it is when it is concentrated into a spark that it is significant. To get ignition, you need 3 things, firstly an ignitable ratio of fuel vapour in air (guaranteed, somewhere around, inside or adjacent to the tank neck, when the cap is off except maybe in very cold weather. Normally the vapour is saturated in the tank, and zero at a distance, somewhere between it will burn). Secondly, a high enough temperature for ignition (surprisingly not an exhaust) and thirdly sufficient energy for ignition (we are probably talking millijoules or less here). So, a very hot, but small and thin spark of nanosecond duration such as static discharge, might do nothing, an almost red hot maniflod usually will not ignite petrol (don't know about unleaded, the old stuff was OK), but a train of mediocre sparks produced as the induced RF jumps the gap between the nozzle and the tank might.
As far as RF is concerned, the frequency matters a great deal. In the UK it would be illegal to use any transmitter of decent power output, but there are issues of where the antenna is positioned, and you will not get much induced voltage on a smallish thing like the pump nozzle at for example CB frequencies.
You are quite correct, and one of the few people on/. today who comprehends the issues. I think the reason they carried on the testing for a while, not one quick pass, was to allow conditions to vary, there would be places around the periphery where the concentration would be about right, and given enough sparks they would hit one eventually. Like the Spedding Steel Mill, it only demonstrated safety on a statistical basis, not an absolute one, and there would be situations where petrol was ignited by a friction spark, it is just that before unleaded at least, they were in the minority. Most fires in cars appear to be electrical in origin, even today, with lots of fuses, but it would be folly to take chances. Perversely, leaded petrol spilled on a hot exhaust manifold would not ignite, but lubricating oil or brake fluid often would, of course in the case of petrol the tiniest source of ignition, sparks at the dynamo brushes for example would then set it off. Knowing that in theory I should be safe, on the one occasion where I had a spill of fuel on a hot engine, I still ran..... It is not worth taking risks.
Ignition is not necessarily optimum at the stoichiometric ratio, that is where full burning is achieved (ideally) with no excess oxygen or fuel left over, AFAIK in the case of petrol, weaker mixtures, up to a point, can be more readily ignited, which is why if your mixture is adjusted too weak, you get detonation and eventually engine damage. Of course, the compression in the engine complicates an already complex issue.....
There was one already this year, caused by a mobile.
But you miss the point. To get ignition, the vapour concentrartion in the air must be within a certain range, whuch varies according to the particular vapour of course. With petrol, you tend to get a sufficient concentration only around the tank filler, exactly where there is intermittent contact between the nozzle and the car, the precise place where RF-induced sparks will occur, and it is far from being a remote risk.
The amount of sparking due to HT leakage on an old car, if the engine runs tolerably well, is probably insufficient to ignite petrol, but you have identified a possible hazard, and it would be prudent not to chance it. Of course, if the plug lead came off, and was flapping around, your scenario could be very realistic indeed, and no doubt has accounted for a fair number of tragedies. But, you would be stupid to park a car over a pool of petrol, if I saw that happen, I would want to carefully push my car away from it, because there are other sources of ignition (starter motor brushes, ignition switch contacts.....) and it is not inconceivable that a dangerous concentration of vapour could build up (not on a windy day of course).
As to those who switch off their phones, not many, which is why accidents happen, The public are not sufficiently well informed to understand the issues, even most of the posters to/. do not seem to have the knowledge to understand the issue, they seem to think, with some justification, that the phones themselves will not ignite petrol, and have no comprehension that the induced field acts on bits of metal near but not necessarily immediately adjacent to the phone.
You are the one who needs to read and learn. What frequency were the radios on? That makes a very big difference, also you can't compare "intrinsically safe" in one application area to another directly.
Their experiment was ill-conceived. Had they simulated the action of poking a pump nozzle into a vapour-filled tank, making light and intermittent contact, they would definitely have had their explosion. The phones do not cause explosions (excluding possible arcing at battery contacts, switches etc), it is sparking induced between bits of metal which are almost touching, as a result of the curent induced by the RF from the phone, that does the damage.
That is why it gets confused with static, the ignition happens in the same place. Some of the fires and explosions due to phones have happened in wet conditions, when staiic charging is impossible.
It is not the paranoia of being sued, it is a clear lack of comprehension of technical and scientific issues that is the problem here. Mobiles are a hazard, they can induce a spark between the pump nozzle and the car, both in theory and in practice. They are known to have caused a number of fires and explosions worldwide, some in Australia. A remote car lock will not. The power levels are very different, the standard car locking transmitter is well below the ignition threshold, the mobile is actually well above it, in certain circumstances, which can realistically occur.
Their experiments were worthless, because they did not replicate the actual source of risk, the metal nozzle being brought lightly into contact with, or almost in contact with, the metal parts of the vehicle. It is the "almost touching" condition that creates the spark when the RF energy from the phone is present. Unless you replicate that, very carefully, nothing will happen. The phones themselves wil not cause ignition (a loose antenna or battery connection might, if in an explosive fuel/air mixture), the ignition can occur several feet from the phone, but almost always at the pump nozzle. The eyewitness accounts and theory are in exact agreement, it is predicted to happen, and it has been seen to happen. Nothing that ill-conceived experiments by a bunch of media people can change in any way
Don't just leave it in the car, switch it off before entering the filling station!
But you are absolutely right about the stupidity of taking the risk, yet most people don't seem to care. The sad thing is that others are also put at risk.
As an expereinced engineer, with much of it involving safety systems, RF hazards and such like, I am fully convinced that the risk is very real indeed. That seems to be the view of most engineering professionals, sadly it is not a view that is shared by the media, or most members of the public, so we will continue to have fires. There was one in the UK recently, not as serious as it might have been.
Our laws involving petrol and other hazardous sunstances have for a long time reflected the established evidence that RF energy, or the sparks it can cause between bits of metal, is a serious risk, yet seemingly no-one actually believes it. Ignorance can be a very dangerous thing.
Yes, they have a lot more training than you, with your ignorant and ill-founded comments, which may result in some unfortunates frying tehmselves if they believe you. A cellphone emits typically 1.5 watts peak, well above the ignition threshold, and there are very many dociumented cases, with eyewitness accounts, worldwide. It is very easy indeed for an electric spark to pass between two bits of metal as they are brought into contact (the nozzle and the car) as a result of the induced RF from the phone, and that, provably, is what happens. (As I have said elsewhere in this topic today, there are anti-static precautions nowadays.) To the ignorant such as yourself, the cause may seem to be static, when in fact it is the phone, The fire will start at exactly the same place.
I suggest that you learn some basic physics before misleading others.
Your pacemaker does not cause sparks between adjacent bits of metal, it is a low frequency thing and will radiate vertually nothing, your cellphone, like all radio transmitters, can and does. Your PDA should, by law, not radiate much energy at all (for reasons of interference to radio and TV etc), it also has no way internally of generating sufficient RF energy to get above the ignition threshold. But, the 1.5 watts peak from a cellphone certainly does!
But possibly the batteries in the PDA, or switches, could present a hazard. If left lying in the car, the PDA is harmless.
These mindless and incompetent tests prove nothing. The cause of the fires is that a spark induced by RF energy from the phone happens to jump the small gap between nozzle and tank. That is how it happens, every single time. The phone needs to be transmitting at the time, and at high power level, which they do periodically. The energy output is well above the threshold for ignition of unleaded fuel.
You can put as many phones as you want anywher eyou like and make them ring, they will ignite nothing unless some bits of metal provide the spark gap. That was not done by the incompetent fools who carried out these tests.
Irresponsible reporting like that endangers the public because it encourages people to think that using them in the wrong place, illegally, is safe, when all the factual and theoretical experience, stretching way back to long before cellular phones were dreamed of, says that it is not.
Fires have been seen starting as the nozzle was put into the tank, which as theory would suggest is the worst condition.
You can also crash it, or any other aircarft, with a knitting needle, I am not going to tell you how for obvious reasons. Suffice it to say that you would need to deploy the knitting needle more than once to overcome the structural and system redundancy provided by the designers.
They are carefully positioned to avoid hazards, unlike roving mobiles, as I have said elsewhere under this topic today. Please read about the inverse square law (try Google) to understand why a separation of maybe 40 or 50 feet makes a huge difference.
There is plenty of fact, eyewitness accounts from all over Europe, including one in the UK a few months ago) confirm that the hazard is very real. It is also supported by theory and experiments dating back to way before cellphones were dreamed of.
Well, maybe, and usually it will go out, but please don't do it to my nice little Focus Turbodiesel, because I don't want my fuel pump ruined by bits of burnt match. But, if you did get the diesel to ignite, it would be self-extinguishing, without an inflow of oxygen. However, on a very hot (and I mean very hot day I would advise caution, there might just about be enough vapour....
And, I do hope you are right, I would be very happy burning vegetable oil from a renewable resource. They tell me it burns cleaner, and is harmless to skin if you happen to spill some. But, at the moment I can't buy it in the UK, not easily anyway.
Not usually, the sparking at the commutator would be very minor, it it was a simple DC motor. (I thing they are usually not, and don't have brushes.) But, an exceptionally large and badly worn one might. However, it is almost always the RF energy which causes the problem, 1.5 watts is well above the safe level for an explosive atmosphere, and many of the phones involved in fires and explosions did not have vibrators!
It is incompetent and ill-informed statements like that which are causing these fires. A piezo-electric sounder is not a voltage step-up device, it has about 2 volts applied to make the sound when the phone rings. The source of ignition is RF energy, it is entirely consistent with theory and such experiments as have been carried out, dating back to long before cellular phones were invented.
The transmitter in the phone can and will cause fires, there are eyewitness accounts to that effect.
If a fire started as the phone rang, it would not be surprising, because the transmitter would not have been operating until that moment. The first thing the phone does, when it receives an incoming call, or on certain other occasions such as when the network wants to know if it is still there, is to transmit at full power, onvce the two-way contact is proven the power level may be trimmed back. So the chances are that the fires and explosions will mostly coincide with incoming calls.
I am properly trained and qualified in EMC, safety, RF hazards etc, and my colleagues, who are similarly qualified and experienced, all share these views.
Slashdot Mirror
Your observations would indicate that it might not happen very often (and indeed it does not) but anything to do with RF, and complex, changing geometry, has so many possible scenarios that wheer the transmitter power is at the level of 1.5 watts, there will be exact configurations when disaster will occur. It is quite a low power level, but well above what is needed for ignition. In some conditions, a fair proportion of the power may well end up where it is least wanted. A few milliwatts in the wrong place is all it takes.
And because something does not happen 99 times out of 100, it does not follow that it can't happen, especially when theory and tests which date back to way before mobiles were invented show that the relevant RF power level does present an ingition hazard.
As for the effcets on aircraft, I am by profession an avionics designer (with a huge amount of safety, RF/EMC, even software, thrown in for good measure. I also have an honours degree in physics. I am well placed to know that all but the very latest aircraft have vulnerabilities in their systems because when they were designed, the threat presented by mobile phones on board, within the fusleage, did not exist. There have been a number of incidents involving uncommanded manoeuvers, and malfuntion of various systems, strangely in every case, the problems went away when the phone concerned was switched off, and returned when it was swithed on again. If that does not constitute proof, I do not know what does, and of course any uncommanded manoeuver could easily turn into a disaster.
For that reason, people who do not switch off their phones while on board aircraft should automatically receieve severe prison sentences, and fortunately at least one UK court agreed, I think the guy got 2 years.
However, as regards the battery theory, if you directly short a charged mobile battery, some types will catch fire or explode after a short while, within themselves, and yes you can produce sparks sufficient to ignite petrol from a small battery, again by means of an intermittent connection, DC is just as effective as RF.
Yes, that is precisely your score, because you have no comprehension of the issues involved. It is people like you, asserting their opinion that danger is in fact safety, from a position of wilful ignorance, that are dangerous. Come to think of it, that is exactly what politicians do, so I guess you must be one. I simply switch off my phone and endanger no-one.
Your experiment is interesting, but does not tell the whole story, you really need to try to make sparks with two bits of metal (one maybe resonant) lightly brushing against one another. You will need good equipment to see the sparks, but if you can devise such an experiment, I think you will be convinced.
You don't need anything like 90 volts.
AFAIK, "intrinsically safe" electrical circuits are limited to a few volta and a few milliamps. If you look up those standards and see how low it does need to be to avoid all risk, and then do some measurements of actual RF voltages with the appropriate instrument, I think you will be convinced.
I have in the past done a fair bit of EMC testing, and when you are appling an external field it is quite amazing what voltages can appear if anything resonates. It does not need more than a few volts to get sustained (but minor) arcing if the conditions are right. Of course where petrol is concerned, a minor arc is all that might be needed.
But, I hope you wil be able to see all this by experiment, it should be fun.
In the UK we don't have latching pump valves any more, at least I have not seen them lately, maybe for this reason. When we did have them, they were regulated by law such that they had to reliably shut off if the back pressure in the nozzle became too great, one of my old cars had a long and narrow neck, and the lever had to be held dowm manualy or it would trip.
I think you have convincingly shown that cell phones are dangerous in filling stations, not just because of the RF hazard!
The "Q" factor of a resonant circuit used to be called the "magnification factor" becaus ethat is exactly what it does. It does not produce energy out of nowhere, but your assumptions about the possible magnitude of theinduced voltages are well off the mark, as you would know if you had ever done any EMC testing, for example.
Also, how vapours ignite is a complex issue, but often a static spark will not do the job (not something to rely on of course) because it represents a fixed amount of energy dissipated in a few nanoseconds. If the pump nozzle is picking up some RF voltage, and is brushing against the neck of the tank, there can be multiple sparks over a short period of time, the actual energy input can be higher, and so the probability of ignition can be higher.
Consider where the signs are in relation to the pumps, and where a mobile might be.....
It is ironic as you say, because it sends the wrong message to the public, who do not understand the issue, and imagine it must be safe to use their mobile 100 times closer to the tank they are filling.
As far as RF is concerned, the frequency matters a great deal. In the UK it would be illegal to use any transmitter of decent power output, but there are issues of where the antenna is positioned, and you will not get much induced voltage on a smallish thing like the pump nozzle at for example CB frequencies.
Ignition is not necessarily optimum at the stoichiometric ratio, that is where full burning is achieved (ideally) with no excess oxygen or fuel left over, AFAIK in the case of petrol, weaker mixtures, up to a point, can be more readily ignited, which is why if your mixture is adjusted too weak, you get detonation and eventually engine damage. Of course, the compression in the engine complicates an already complex issue.....
But you miss the point. To get ignition, the vapour concentrartion in the air must be within a certain range, whuch varies according to the particular vapour of course. With petrol, you tend to get a sufficient concentration only around the tank filler, exactly where there is intermittent contact between the nozzle and the car, the precise place where RF-induced sparks will occur, and it is far from being a remote risk.
The amount of sparking due to HT leakage on an old car, if the engine runs tolerably well, is probably insufficient to ignite petrol, but you have identified a possible hazard, and it would be prudent not to chance it. Of course, if the plug lead came off, and was flapping around, your scenario could be very realistic indeed, and no doubt has accounted for a fair number of tragedies. But, you would be stupid to park a car over a pool of petrol, if I saw that happen, I would want to carefully push my car away from it, because there are other sources of ignition (starter motor brushes, ignition switch contacts.....) and it is not inconceivable that a dangerous concentration of vapour could build up (not on a windy day of course).
As to those who switch off their phones, not many, which is why accidents happen, The public are not sufficiently well informed to understand the issues, even most of the posters to /. do not seem to have the knowledge to understand the issue, they seem to think, with some justification, that the phones themselves will not ignite petrol, and have no comprehension that the induced field acts on bits of metal near but not necessarily immediately adjacent to the phone.
You are the one who needs to read and learn. What frequency were the radios on? That makes a very big difference, also you can't compare "intrinsically safe" in one application area to another directly.
That is why it gets confused with static, the ignition happens in the same place. Some of the fires and explosions due to phones have happened in wet conditions, when staiic charging is impossible.
It is not the paranoia of being sued, it is a clear lack of comprehension of technical and scientific issues that is the problem here. Mobiles are a hazard, they can induce a spark between the pump nozzle and the car, both in theory and in practice. They are known to have caused a number of fires and explosions worldwide, some in Australia. A remote car lock will not. The power levels are very different, the standard car locking transmitter is well below the ignition threshold, the mobile is actually well above it, in certain circumstances, which can realistically occur.
Their experiments were worthless, because they did not replicate the actual source of risk, the metal nozzle being brought lightly into contact with, or almost in contact with, the metal parts of the vehicle. It is the "almost touching" condition that creates the spark when the RF energy from the phone is present. Unless you replicate that, very carefully, nothing will happen. The phones themselves wil not cause ignition (a loose antenna or battery connection might, if in an explosive fuel/air mixture), the ignition can occur several feet from the phone, but almost always at the pump nozzle. The eyewitness accounts and theory are in exact agreement, it is predicted to happen, and it has been seen to happen. Nothing that ill-conceived experiments by a bunch of media people can change in any way
But you are absolutely right about the stupidity of taking the risk, yet most people don't seem to care. The sad thing is that others are also put at risk.
As an expereinced engineer, with much of it involving safety systems, RF hazards and such like, I am fully convinced that the risk is very real indeed. That seems to be the view of most engineering professionals, sadly it is not a view that is shared by the media, or most members of the public, so we will continue to have fires. There was one in the UK recently, not as serious as it might have been.
Our laws involving petrol and other hazardous sunstances have for a long time reflected the established evidence that RF energy, or the sparks it can cause between bits of metal, is a serious risk, yet seemingly no-one actually believes it. Ignorance can be a very dangerous thing.
I suggest that you learn some basic physics before misleading others.
But possibly the batteries in the PDA, or switches, could present a hazard. If left lying in the car, the PDA is harmless.
You can put as many phones as you want anywher eyou like and make them ring, they will ignite nothing unless some bits of metal provide the spark gap. That was not done by the incompetent fools who carried out these tests.
Irresponsible reporting like that endangers the public because it encourages people to think that using them in the wrong place, illegally, is safe, when all the factual and theoretical experience, stretching way back to long before cellular phones were dreamed of, says that it is not.
Fires have been seen starting as the nozzle was put into the tank, which as theory would suggest is the worst condition.
You can also crash it, or any other aircarft, with a knitting needle, I am not going to tell you how for obvious reasons. Suffice it to say that you would need to deploy the knitting needle more than once to overcome the structural and system redundancy provided by the designers.
They are carefully positioned to avoid hazards, unlike roving mobiles, as I have said elsewhere under this topic today. Please read about the inverse square law (try Google) to understand why a separation of maybe 40 or 50 feet makes a huge difference.
There is plenty of fact, eyewitness accounts from all over Europe, including one in the UK a few months ago) confirm that the hazard is very real. It is also supported by theory and experiments dating back to way before cellphones were dreamed of.
And, I do hope you are right, I would be very happy burning vegetable oil from a renewable resource. They tell me it burns cleaner, and is harmless to skin if you happen to spill some. But, at the moment I can't buy it in the UK, not easily anyway.
Not usually, the sparking at the commutator would be very minor, it it was a simple DC motor. (I thing they are usually not, and don't have brushes.) But, an exceptionally large and badly worn one might. However, it is almost always the RF energy which causes the problem, 1.5 watts is well above the safe level for an explosive atmosphere, and many of the phones involved in fires and explosions did not have vibrators!
The transmitter in the phone can and will cause fires, there are eyewitness accounts to that effect.
If a fire started as the phone rang, it would not be surprising, because the transmitter would not have been operating until that moment. The first thing the phone does, when it receives an incoming call, or on certain other occasions such as when the network wants to know if it is still there, is to transmit at full power, onvce the two-way contact is proven the power level may be trimmed back. So the chances are that the fires and explosions will mostly coincide with incoming calls.
I am properly trained and qualified in EMC, safety, RF hazards etc, and my colleagues, who are similarly qualified and experienced, all share these views.