Conclusions
Based on our analyses, the ignition of flammable vapors at a gasoline station by a cell phone is a highly unlikely event. While the cell phone cannot be ruled out as a potential ignition source under all physically possible scenarios, numerous other more likely ignition sources are present during the normal process of refueling a vehicle. This conclusion is supported by the following observations:
1. No confirmed incidents of fires at gasoline stations started by cell phones have been found.
2. Combustible vapors produced during fueling will not generally collect in regions of probable cell phone operation.
3. The small openings present in a typical cell phone’s casing will limit the concentration of any combustible vapors present within the cell phone. In addition, narrow gaps may quench any flames if they are ignited internally, preventing their propagation outside the enclosure.
4. A combination of events would have to occur in order to create an accident, including:
a. the placement of the cell phone in a flammable mixture for a sufficient length of time to allow a flammable mixture to form inside the cell phone,
b. a fault, malfunction, or spark generation in the cell phone that would produce a competent ignition source that could propagate outside of the battery or phone enclosure.
(A spill or dispersion of liquid gasoline on or near the phone would increase the hazard by increasing the likelihood of having combustible vapors present at the ignition source.)
5. Automobiles and the process of refueling provide potential ignition scenarios that are more likely to result in flammable vapor ignition.
In summary, the enclosures protecting the battery and cell phones, the low voltages and current drains of these components, the geometry of their interconnections, and the physics of electrical discharge and vapor diffusion strongly direct against the cell phone and battery acting as an ignition source while at a service station.
