The hazards of static electricity
Static electricity incidents have occurred in recent years which have highlighted concerns about explosion or fire while transferring vehicle fuels. These may indicate that changes taking place threaten the existing precautions for controlling these hazards. It is a well-known phenomenon that if two materials are rubbed together, static electricity is generated and electric sparks can be produced. Common examples are walking across a nylon carpet and then touching a metal surface such as a hand-rail when an alarming (but harmless) shock can be felt. Also, removing nylon clothing in the dark can generate an impressive display of sparks. What is perhaps less well known (outside industry) is that the same phenomenon can occur with liquids, including gasoline, kerosine and diesel, which are poor conductors of electricity. Static discharges (e.g. lightning) can also be generated by water drops passing through the air. Although much smaller voltages than lightning are developed, water washing (and indeed fire-fighting sprays) can generate enough charge to ignite flammable liquids.