Not really, I never gave it much thought. Where I grew up its pretty common. I probably have done it over 100 times.
My point is that if it could lead to an explosion there most likely be some kind of stop involved for liability reasons, but as you point out, thats not always true.
I’ll have to research and see if gasoline fumes are lighter than air or not. While I was exaggerating for effect in my post above, I did think that gas fumes tended not to hang around in open air for very long at all (cf. helium).
They are heavier than air, which is part of what causes problems when pouring gasoline indoors. In the absence of any dispersive breeze the fumes tend to collect on the floor and then flow across the floor to ignition sources (e.g. water heater pilot lights) that were thought to be safely far away.
In my very limited understanding of engines, I thought the spark plugs are very isolated from the outside world. I think the danger of igniting the fumes are VERY low. Of course, you get every one of those millions of fill-ups going with running cars, even a 99.99% safety record would result in a fair number of fatalities.
As long as everybody mostly fills up with the engine off, I think the danger of dying while filling up falls somewhere in the realm of dying in a collision with livestock or other highly unlikely danger.
Yup, per pg 3 of this Material Safety Data Sheet (PDF):
Although the way the MSDS explains it, gasoline fires/explosions should be super-common. Essentially, a person smoking a cigarette a mile away from a gas station should be able to set fire to any wafting gasoline vapors that may happen to be in the air. Yet this doesn’t happen 
This report is 10 years old. It goes without saying that cell phone technology has advanced and to compare the phones of 10 years ago with the phones of today is a poor comparison. This is not to assert that cell phones now present some ignition hazard that older phones did not, however I do not make this assertion.
I will, however, point out that the military does not allow cell phones near many types of ordnance, and has EM certification stickers that must be placed on phones that are allowed near ordnance. Draw from this what you will.
For Rick. A Cite:
Texas Department of Transportation and EPA.
I’ve done it numerous times. While it’s not something I would make a habit, I don’t really see much danger. Pumps don’t emit a lot of fumes, and what little bit is emitted will go toward the ground near the back of the vehicle. I’ve seen people do far more dangerous things with gasoline, such as pouring it on brush then going downhill to light the match.
Actually, it’s practically impossible to light gas with a cigarette. You can drop it in gasoline and it won’t ignite. Of course, a match or lighter will ignite gas, but not a lit cigarette.
I have heard of that, too … maybe that’s the factoid that gets twisted around when gasoline vapor risks get pooh-poohed.
So, is a cigarette not hot enough? From the same MSDS I posted above:
Ordnance may have fuzing controlled by electronics, so EMI could cause the electronics to malfunction and inappropriately detonate the ordnance.
True story:
In a former life, I designed simulated ordnance used for training purposes. (google MILES gear for examples) In some cases we equipped vehicles with pyrotechnics to indicate when the vehicles were “hit”.
One of these vehicles “went off” in a Wendy’s drive-thru, which caused all kinds of feces to contact the rotary oscillator. It was concluded that the wireless headsets used by the Wendy’s staff were the cause.
As a result, extensive RF filtering was added to these systems. This happend before I joined the team. I eventually traced some later malfunctions (failures to “go off”) of the equipment to this filtering, so I got to see the documentation for the incident discribed above.
Spark plugs are isolated but alternators aren’t and a defective one could potentially produce sparks, as could defective HT leads.
Still the risk has to be minimal or a car pulling in next to you while you refuel, or one starting up and leaving, could generate sparks and cause vapours to ignite.
More so the second alternative as a starter motor is much more likely to generate sparks than anything else.
That said, the petrol vapour mix with air is fairly critical with regard to combustion.
But those cases aren’t really analogous at all.
Texting on mobile phones has only been around for a decade or so, and only popular for half that time, yet laws are already cropping up prohibiting it in many places. It wouldn’t surprise me if, in 10 years time, phones will be able to tell if you’re in the driver’s seat and prevent you from using them while the car is in motion. The law and safety regulations lag a bit behind technology.
In contrast, we’ve been driving and fueling petroleum-based vehicles for over 100 years. There are thousands of safety regulations required in cars, and the ones required to prevent this sort of thing are trivial from an engineering perspective. It’s not at all unreasonable to assume that if it were really dangerous, there would be safety locks in place to prevent it.
The bill against texting while driving in Wisconsin is almost law. It’s waiting for the governor’s signature and he’s going to sign it.
I’m a little surprised that so many of you find leaving the engine running while refueling unusual. Maybe it’s because I live in one of only two states where filling your own tank isn’t allowed? Here in NJ, in my experience, leaving the engine running while re-fueling is the norm. I’ve been driving for a long time and I had a job pumping gas as a teenager and almost everyone leaves their engine running.
As an interesting side note, since race car fueling was mentioned above, here is an article about how fuel is handled by the car when it is added in F1:
http://formula-one.speedtv.com/article/matchett_life_inside_a_formula_1_fuel_tank
Also, race car fuel fillers are often pressurized. If you want to know what happens when something goes wrong, though…: http://www.youtube.com/watch?v=WBPOqODqYB0
If a running car poses such a risk to ignighting gas fumes then everyone should cringe while refueling as other vehicles come and go nearby.
No, a cigarette (~450 deg F) is not hot enough to ignite liquid gasoline. However, gasoline vapor may ignite at much lower temperature; the flashpoint (the temperature level at which it will outgas enough to allow combustion) is actually significantly below the freezing temperature of water. The reason for this is that liquid gasoline will conduct away heat influx below the liquid ignition temperature into the interior mass, which is not exposed to air and will not combust (until you get to a chemical degradation temperature, which is significantly higher than the ignition temperature). This rapidly equalizes the temperature and prevents any small localized combustion that would result in sustained critical combustion of the entire mass. However, vapor consists of individual molecules that are distributed in air in some approximation of stochiometric mixture, and any localized heating or small spark can result in exothermic reaction that can cause ignition of nearby molecules, ad nauseam, resulting in a large fireball. This is the principle that fuel-air bombs are based upon.
While it is fairly unlikely that enough gasoline vapor from auto fueling will collect in an open area to cause combustion (especially with modern vapor traps on fueling nozzles) it has happened on occasion that vapors have caught fire from electrostatic discharge or open flame. This is more likely when fuel or fuel systems are in confined areas, like buildings or within the hull of a boat, hence why any such compartments should be positively ventilated, like blowers on a boat. (Smart sailors will run the blowers on the engine compartment, whether the engines are gasoline or diesel fueled, even though diesel fumes will not ignite.) This is far less of an issue with the less vaporous and higher flash point fuels like automotive diesel, kerosene, and JP/avgas, and yet, safe fueling procedures for vehicles using these fuels still require positive ventilation, no flame or sparking, and engines stopped. (Diesel engines in cold temperatures are often left running because of the possibility of fuel gelling in the lines.)
So it is not an unreasonable safety precaution to stop engines and suppress any open combustion
Stranger
the biggest hazard is static discharge by the driver at a self service pump. depends on the fabric of their clothes and seat material they can build up a static charge and it will discharge when grounded as might be when touching the fuel nozzle. initially when you get the nozzle from the pump you discharge yourself, there are likely no explosive fuel vapor mixture about so no explosion.
if you get back into the car to stay warm or listen to tunes because your engine is running and then you get out again with a fresh static charge and the first grounded thing you touch is the nozzle and you might have a static discharge, the nozzle can be surrounded by an explosive fuel vapor mixture coming out of your filler tube and then you might have an explosion.
if you come out of a car during fueling you should touch the metal pump first to discharge yourself.
nearby cars don’t pose a hazard because the vapors are too dilute when it reaches them. pump attendants don’t pose a hazard because they’ve discharged themselves at the pump and aren’t sliding on the seats.
Ironically, while driving. There’s no law against that.
OK, I have read the entire link. Where in there does it say that removing your gas cap while the engine is running will damage your pollution control system? Which system on which car, that is what I want a cite for. In case you forgot, here is what I am asking for a cite on.