- The Washington Times - Friday, August 9, 2002

We Americans visit the fuel pump 16 billion to 18 billion times a year. Few activities are more familiar than dispensing gasoline into vehicles at neighborhood stations or along interstate exits.
Although gasoline is a potentially dangerous substance, most of us rely on the built-in safety of filling equipment both in the vehicle and at the pump. Fires at the filling station are uncommon, but they do occur.
Until recent years, the only motor-vehicle-refueling fires that the Petroleum Equipment Institute (PEI) was aware of were caused by one of three things: open flames (smoking, etc.), lack of electrical continuity between the nozzle and dispenser, or a spark from the engine compartment of a vehicle with its motor running (that's why all pumps are posted with the requirement that engines must be off).
Recently, however, the PEI has researched 150 cases of fires that were not caused by the "normal" reasons. In all of these cases, investigators concluded that static electricity was the source of ignition. There were, however, a number of similarities found in the majority of cases. Examining these showed some interesting and even surprising facts:
Out of 150 cases, almost all the drivers were women.
Almost all cases involved the driver getting back into the vehicle while the nozzle was still pumping gas. When the pump shut off, drivers went back to pull the nozzle out and the fire started as a result of static discharge.
Most wore rubber-soled shoes.
Almost all the fires occurred during dry weather (most between November and March).
No particular make or model has a significant rate of incidents.
Static electricity can be built up a number of ways and seems to be the primary source of the spark that ignites gasoline vapors in certain conditions. Some of these conditions could include the following:
Fuel chemistry might have changed in a way that altered its electrical conductivity in certain atmospheric situations. Tests by the petroleum industry are continuing.
The paved surface of the refueling area might create triboelectric effects with the vehicle's tires. The triboelectric effect is what occurs when two differing materials are rubbed together, producing high voltage. The most common example is walking across the carpet in socks and then touching the light switch. Up to 3,000 volts can be generated in this way.
Electrostatic charges can be generated through friction between the car seat and the owner's clothing, especially when the customer is wearing rubber-soled shoes. The shoes prevent static discharge to the pavement, increasing the likelihood that the spark will occur at the gasoline filler.
Vehicle filler inlets are increasingly made of plastic. Although plastics are nonconducting, it is possible that refueling can transmit a charge to the filler neck that, in turn, might cause a spark to jump to the grounded nozzle.
Cell phones generate electromagnetic radiation that, under the right conditions, could create an electrostatic charge.
However unlikely a gasoline fire might be, there are things you can do to ensure you won't be involved in one of those rare instances. Don't get back into the vehicle once filling has started. If you must do so, touch some part of the vehicle's metal before going back to the filler. Make sure the engine is off, and don't talk on the cell phone or two-way radio while filling.

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