I recently noticed the fine-print warning at the gas pump about the risk of fire from static electricity sparks. How serious is this? – Tatum in Campbell River, B.C.
You're probably more likely to be struck by lightning, but in certain circumstances, the static electricity you carry out of your car can ignite gasoline vapours at the pump.
"When you exit the car, first of all you're going to open your door, and when you touch the door you're no longer charged," says Bob Renkes, executive vice-president at the Petroleum Equipment Institute in Tulsa, Okla.
"Then you're probably going to touch the nozzle to get it out of the boot. You may use a credit card, you're going to touch that, too. Usually there's a door on your car that gets you to the fill cap, and you're going to touch the cap. So you have seven or eight times when you'll dissipate your static electricity – and all it takes is once. So we never have a problem when we initially fuel."
Renkes, who began investigating fires during refuelling 11 years ago, found the real risk is for motorists who re-enter their vehicle once the fuelling process has begun.
"These people are sitting in their car and then pivoting 90 degrees to the left and popping out without touching something. So fuelling is going on, you're in your car, you move around – you're checking on your child, getting out of the cold, checking the odometer reading, or returning a credit card to a purse," says Renkes.
"So they're sitting in the car, they generate static, they pop out again, they haven't dissipated their static, and they touch their nozzle. As gasoline goes in, the vapours come out of the fill pipe, so you have a source of ignition when your static discharges from your hand to the nozzle – exactly where the vapours are coming out of the fill pipe. So it does happen," says Renkes.
An eye-opening example of this can be seen at pei.org/static, in footage from a gas station surveillance camera.
The technology in newer vehicles, however, lessens this potential risk.
"In the old days you used to say, 'Boy, I love the smell of gasoline' whenever you refuelled. You don't have that anymore. You can't smell the vapours because they're not coming out. Newer cars have what's called an onboard vapour recovery system, which pushes the vapours to the engine component where they're stored in a carbon canister and burned when the car goes on. If you have onboard vapour recovery, you don't have the vapours coming out of the fill port. Instead of being pushed out of the gasoline tank, they're pushed to the engine compartment. But if you have an older car without vapour recovery, in colder climates where it's dry, you can still have static discharge. So our rule is: don't get back in your car while refuelling. If you must, touch a piece of metal away from the filling port before you touch the nozzle," says Renkes.
Again, it's extremely rare, but if a fire does occur while refuelling, resist the temptation to remove the nozzle from your vehicle. Rather, step away and the attendant will shut off the pumps using emergency controls.
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