Fire Chief Convinced Cell Phone Sparked Gas Station Blaze
vs.
Snope’s Urban Legends Reference Pages Cited in Above Story
The fire chief does not have enough information to make such a determination. Just because the fire started at about the same time the victim answered his cellphone does not mean the phone must have started thefire. Post hoc ergo propter hoc, is a common logical fallacy. It’s far more likely that a static disharge ocurring at about the same time is the real culprit, IMO.
The Snopes page has been updated.
From the link (scroll down past the main article):
I’ve got to agree with Q.E.D. on this one. Unfortunately, in the fire service there are times when the easiest factor to blame is tagged, rather than performing an exhaustive investigation.
One of my professors used to quote: Correlation does not prove causation.
Is believed it that sparks from within the phone are causing the fires or is the phone inducing sparks remotely?
The article says that the fire started aroound the nozzle.
Well, it’s a bit odd, because May isn’t a time of year when you’d expect to see a lot of static electricity – usually the humidity is high enough to keep the sparks down. Still, if the guy had to answer his phone, it might be worth investigating what kind of case he kept it in, and whether there’s a velcro strip or some synthetic materials that might have caused a spark.
Why would answering a phone cause enough of a spark to light gasoline when the phone ringing did not?
Probably because most people have no idea how things work.
In order to ignite gas fumes, you need two things: sufficient fume concentration and an ignition source, right?
An ignition source could be a spark or a very hot surface. I don’t know just how much fume concentration would be needed, but let’s conduct a (virtual, not real) experiment. Let’s say you have a spark creator in a fireplace starter gadget, and a can of gasoline. Let’s say you have both in an unenclosed outdoor environment. You flick the sparker 100 ft from the can of gas. What happens? Nothing. Oh – you forgot to open the can. Open it, flick – still nothing. Now move closer, try it again, until it explodes. How close do you think you would have to be? My guess is right at the nozzle, because the fumes expand as soon as they leave it.
Now a celphone doesn’t normally create external sparks or high heat, and the user in this story didn’t shove it down the pipe anyway. I think if he could stand next to the car without being overcome by fumes, they were probably quite minimal. It seems unlikely that the celphone is the culprit.
Probably the reason his phone rang was someone calling – “Dude, your car’s on fire!”
Your query regarding concentration of vapor and ignition source, Musicat is valid.
Per NIOSH: gasoline has a lower explosive limit of 1.4% and an upper explosive limit of 7.6% which strongly suggests to me that the vapor concentration present at the filler neck of the vehicle was well above the UEL.
While not a cellular phone technician, my electronics knowledge indicates that keystrokes draw microamperes-the major power draw from a phone is sending/receiving the RF signal and backlighting display.
While unable to prove it, my bet is that oil companies simply want you to pay attention when fueling your vehicle, as is reasonable, and cellular use is a distraction, hence their ban on use while fueling.
It’s also a variation on Pascal’s Wager, similar to the prohibition of electronic devices on planes during takeoff/landing – even if the chance of an explosion is .00000…01% of something, why take the chance at all?
As far as celphones and electric currents go, you can have all the current you want coursing thru the circuit boards and chips, but unless it heats something up to Too-Darn-Hot or you can coax electrons to jump an air gap, causing a spark, there’s no danger to a low concentration of volatile vapor.
If the fire started at the nozzle then it’s extremely likely that a static discharge was to blame, not the cell phone.
I can think of a few ways that a cell phone might cause a fire. If the battery had a loose connection maybe you could get a spark as it connects and disconnects. I doubt the phone would work properly, so I doubt someone would be able to answer a phone if this was happening. More likely they would be whacking the side of the phone trying to figure out why the display keeps going on and off. If a capacitor exploded (not likely, but possible) it would make a small, brief flame. If something shorted out, it could cause a component or even a track on the circuit board to make a small, brief flame or spark.
Unless you have some sort of focusing device, there is no way the RF is going to put enough energy anywhere to make a spark.
The chances of a cell phone failure occuring while pumping gas is going to be so low that I don’t know if we’ll ever see a pump fire that is conclusively caused by a cell phone.
I personally think the oil companies were quick to put up cell phone warning signs because (1) it got a bunch of people off their back, (2) it prevented stray RF from the cell phones from affecting the microcontrollers inside the pumps (hey cool, I pumped 30 gallons of gas and it only charged me 4 cents!), and (3) as previously mentioned, it’s one less distraction to prevent you from focusing on what you are doing.
Here is a transcript from ABC TV’s Media Watch. It is interesting to see how these things are propogated.
My initial thought exactly. An hour south on New Paltz, it was as humid as Louisiana both Thursady and Friday. Even though the story isn’t clear - wouldn’t the static electricity threat be highest upon the insertion of the nozze into the tank or at the point the nozzle was removed from the car?
I wonder if anyone will espouse the God doesn’t like Mayor West’s SSM policy and shot a lightning bolt from above
Static can be generated without regard for humidity by the movement of fluids and gases. If you’ve ever used a shop vac and noticed dust and small pieces of debris clinging to the intake hose, the static charge is what holds the particles there. Fuel station hoses have a drain wire within the protective sheath connecting back to earth as a means of removing the charge. Other devices employ this feature, as well-my airless paint spray unit came with precautions about using proper static conductive hoses. If you’ve ever observed a tank truck delivery at a fuel station, grounding/bonding conductor attachment is done prior to product discharge, and is the last thing undone prior to departure of delivery vehicle. Several questions covering this are part of the CDL HazMat endorsement renewal test which I take every 4 years.
Mythbusters did a show on this. They sprayed gasoline vapors into a closed chamber, put a cell phone in side, and then called it. While not definitive, their experiements cast considerable doubt on the cell phone/gas ignition hypothesis.
After they failed with the cell phone, they moved on to using a spark plug to try and ignite the gas. (I think they also tried to generate a static charge rubbing a pair of panties on a glass rod, but let’s not go there.) It turns out that, even using an open flame as an ignition source, they had to tweek the fuel/air mixture just so to get it to work.
ABC News just did a piece on this via Good Morning America, with firefighters testing the theory. Conclusion: firefighters have been unable to start a fire with a cell phone near a fule tank or nozzle.
They had no problem starting fires with discharge of static electricity. It’s most likely a static electricity event…and the driver was using the cell at the time.
Also, leave the nozzle in the car and the flames will likely be supressed.
Did they try to repeat the cell-phone ingition attempt after getting the right mixture?
If they had the wrong mixture the whole time they tested with the phone, then I’d say it’s inconclusive. Of course, then you have to check if the combustable mixture can happen at the pump, and not just in the lab.