"Gas can/static sparks/BOOMS," real or media creation

I’ve seen warnings about filling gas cans on the ground, not the bed of the truck.

The reason is that a charge can build up in the bed or the can, and a spark of static electricity can make a big KA-BOOM.

Is this “real” (as in has it actually happened), or is it along the same lines as the cell phone/gas station explosion scare?

There can be a sufficient voltage difference between a vehicle and the ground to cause a spark. For that matter, there’s you can create enough voltage just by scuffing your feet across a carpet. The safety issue is that you don’t want the spark near the gasoline vapors. So, yes, it is possible – not terribly likely, but possible. And whatever you do, don’t scuff your feet on carpet before filling the gas can!

I once had a short briefing about being rescued from water by helicopter. (We were going to fly in a “test” aircraft (a 767!), but there was no real danger.) They emphasized that you were likely to get a shock from the ladder or whatever they lowered to you because of the voltage difference between the ground and the helicopter.

“If ignorance were corn flakes, you’d be General Mills.”
Cecil Adams
The Straight Dope

Keep this in mind (a quote from the Los Angeles City Fire Department): “One gallon of gasoline, in vapor form, has the explosive power of 83 pounds of dynamite.”
I’ve heard that people who want to repair gasoline tanks with welding, will first fill the tank with water, in order to drive the gasoline vapors out.

The cell phone ban is bullshit. Bullshit, bullshit, bullshit. There’s more spark going on with the spark plugs, with the starter, with the fucking RADIO than there is with a cell phone. I don’t care what you fucking say, you cannot convince me that I am creating a fucking hazard by using a cell phone at a gas station.


We are the children of the Eighties. We are not the first “lost generation” nor today’s lost generation; in fact, we think we know just where we stand - or are discovering it as we speak.

*Homer: The cell phone ban is bullshit. Bullshit, bullshit, bullshit. There’s more spark going on with the spark plugs, with the starter, with the fucking RADIO than there is with a cell phone. I don’t care what you fucking say, you cannot convince me that I am creating a fucking hazard by using a cell phone at a gas station. *

Today, I noticed the “no cell phone” pictograph when I got a fillup, right below the “no smoking” one. Then I turned around, and the station attendant was walking around the pumps with a lit cigarette!

If you place the container on the ground, and keep the nozzle in contact with the container, you will not generate a static spark. When filling flamable liquids in industry, the containers must be bonded to each other (a cable connects each of them together), and the whole collection of containers is grounded. All to stop static sparks.

If, however, you take your plastic gas can and place it on the plastic bed liner of your pickup truck, and pour the gasoline into the container without being in contact with it, you will develop a big difference in charges between the ground/truck/nozzle/can. Your chances of getting a spark are quite good when you connect two of them together. Anytime you take a flamable liquid as potent as gasoline, confine it in a can, and subject it to a spark, you’re going to get a boom.

And no, this isn’t like the cell phone scare. There have been at least a half-dozen fires caused by improper filling of gas cans in plastic bed liners.
Keep those cans on the ground, people.


If your red lights are melting, you’ve parked too close.

Yeah, Chevron and Ford issued a joint press statement about the cans on bedliners issue. I thought at the time that no fires had occurred, but I might be mistaken.

The cell phone thing is an extension of the ban on radios in some blasting zones. A piece of metal just the right length (half-wave dipole, probably) will act as a great antenna and suck up enough energy to generate a fume-igniting spark.

Your ignition system and radio, etc., are under the hood and in the passenger compartment, out of harm’s way. I, for one, see no need to hold a fuel-spewing hose in one hand (easy, now) and a potential spark generator in the other. Talk about evolution in action.

One day a few months ago, we were working on my car, and the work we were doing involved draining the oil. My uncle was draining the oil while smoking. I chastised him for it, and he told me to shut up, it wouldn’t do anything. I told him to prove it, so he took the pan full of dirty oil, and stuck his cigarette right in it. The oil extinguished the cigarette. Then he held the cherry of a new smoke to the surface of the oil, and again, it didn’t catch up. Then, he got some gas in a pan, and did the same thing. He said that the only way either of them would light is from an open flame.

He may have been high on fumes when he did it with the gas, but the oil thing, I can understand.


Homer, your uncle is a bit off track. It’s not so much the presence of an open flame but presence of flammable vapor. Heavy grades of petroleum such as motor oil have high flash and fire points, they are not easily ignited at room temperature. Gasoline has a low flash point and produces flammable vapor at room temp. The cigarette trick works differently with gasoline, disastrously so. FWIW a lit cigarette is an open flame.

Either way it’s an extraordinarily bad idea to smoke when working on cars. You probably won’t change his habits but keep an extinguisher handy when working with him. He may thank you for it someday from his bed in the burn ward.


You wrote:

Ummm… how do I put this delicately???


In the real world your piece of metal would have to be a tiny filament, wrapped just the right number of turns around a ferrous core, with just the right gap. To control this gap, you would need an insulator of the right thickness and this insulator would have to have enough porousity to allow the gasoline fumes and a reasonable amount of oxygen to penetrate. The cellphone would have to be operating slightly out of spec such that it’s power output was about ten times higher than normal and you would have to have a parabolic reflector attached to the cellphone antenna to focus the bulk of the energy at your receiving antenna. Oh yeah, just one more thing, you have to get the transmitting antenna within 1/4 wavelength of the receiving antenna and all this has to occur in the presence of ignitable fumes…

Is it theoretically possible? Yes. Is it probable? No.

How so? Most of my ignition system is fully exposed to potentially explosive fumes in the atmosphere, as are the motors in my power windows, the solenoids in my electric door locks, and most importantly my body which has a tendancy to build up static electricity and I’ve noticed on more than one occasion static discharge when I touch my car door. Really, there are hundreds of more probable sources of flame igniting sparks…


I’m pretty sure the ban on two-way radios in blasting zones isn’t because the radio itself could ignite the explosives, but in case your transmitter accidently caused the radio-controlled detonator to set off the explosives. There isn’t a problem with normal car cardios, just two-way radios (with a transmitter).

As for the cell phone/gas station scare- I don’t think you’d find many engineers that would claim it can NEVER happen, but I’d guess you’re more likely to be struck by a meteor while pumping gas than blown up by your cell phone :slight_smile: The scenario I heard was that if you jostle or drop your cell phone, it’s possible that the battery could briefly become disconnected from the battery terminals, causing a spark (also when the battery immediately reconnects). This actually happens frequently with my phone from normal handling (my battery doesn’t fit too well). According to this theory, not only can you not use the cell phone, you can’t even have it on! I can’t deny that this is possible, but I’d be on the lookout for meteors before worrying about the cell phone.

I wonder how many more lives on average would be saved if Exxon and others donated the money to the American Cancer society, or to local rescue squads, instead of putting millions of cell-phone stickers on gas pumps?


Quickly, first: y’all are totally right about the level of unlikeliness.

JoeyBlades: I figured that even the low wattage associated with a cell phone could translate into a high-voltage, low-current spark with no problem. I also don’t see that you MUST be within 1/4 wavelength (which for cell phones means practically touching).

Arjuna34: yeah, after I posted I suspected that might be a more likely reason, but I have a mental block against real-world use of radio detonators. They let you get to a safer distance than a wire, but in the meantime you’re apparently at the mercy of passing motorists with radios and cell phones… Excellent point about a better way to spend all that money.

In short, it was pre-coffee and I was silly. Remembering a roommate’s discussion of Marine aircraft ordnance detonators (even the impact type) being carefully guarded against EM radiation led me astray.

I.V.E.: My dad is in weapons safty for the navy, and you are right about them guarding against electromagnetic radiation. But you have to realize that you can cook someone in front of a ship’s radar. They used to have a demonstration where they put flash bulbs in a circle 100 yards (or so) away from the radar and let the sucker spin. (I think these were those square bulbs that you could only use once.) All the flash bulbs would fire off as the radar went around. I suspect they are far less concerned with cell phones.

On the other hand, I once heard a story that electric wheel chairs had a problem with police scanners and digital cell phones. It seems that if the little joy stick wasn’t properly sheilded, the radio signals could cause the chair to go off in some random direction.

???I hope we are talking heavy duty and/or expensive tanks here… I can’t imagine taking a torch to a 10 dollar gas can. True Value can’t be THAT far…

so you found a girl who thinks really deep thoughts. what’s so amazing about really deep thoughts? Tori Amos

I believe dougie was referring to industrial tanks. My grandfather was a welder, and did this type of repair on tanker trucks on occasion. Rather than fill them w/ water, however, he said that they “boiled the tank out” w/ steam from a boiler. (Keep in mind this was many years ago. I don’t know if this is still done.)

heh. this reminds me of a story my family tells about my dear, departed grandfather. this is off-topic, but still.

It was the 1950s or 1960s, and apparently, his home had a gas leak somewhere outside. The details are sketchy, but it goes something like this:

He called the gas company to report the gas leak. Gas company representative comes out to the house. Gas company guy asked where my granfather believes the leak is occurring. He leads him to the location, then lights a match to show him the leak. Gas company guy wigs out and runs away hehe.


You wrote:

Frankly it’s not my field of expertise, I just read this in a paper talking about Heinrich Hertz’s experiments in these matters. Hertz was trying to transmit a spark from one antenna to another and this was one of the constraints he discovered. He then went on to find that he could get the spark to jump at further distances when the receiving gap was exposed to UV light and even greater distances were realized when the gap was replaced with crystal… These were, of course, the early days of radio.

I was hoping you’d notice that…

I remember Hard Copy or one of those shows doing a segment on gas cans exploding. I remember them talking about a guy who was either burned really bad or died. Then they showed the journalist in the back of truck with a light bulb. For an example, they turned out the lights and when he touched the (I think) carpet in the truck, the bulb lit up.