"There are numerous references in the model fire codes and standards that refer to the use of 'nonsparking' tools in hazardous environments. These areas may include explosives and pyrotechnic manufacture and storage, flammable liquid or gas production or storage, power stations, pipelines, pharmaceutical production and plastic manufacturing. This list is not exhaustive. Commonly used hand tools are often manufactured of steel alloys. They can cause ignition by friction, with impact on each other or on other materials such as steel or concrete, in which an ordinary mechanical or frictional spark is generated. They also can cause ignition by a chemically generated spark, caused by impact between certain metals and some oxygen-containing substances (such as rust, which is iron oxide)."
Coffee Break Training - Fire Protection Series No. FP-2013-15
United States Fire Administration: http://www.usfa.fema.gov/