Hazardous area indicators are used in situations where the presence of a spark could cause an explosion due to flammable vapours or particles being present in the environment, such as coal dust in a coal mine.
In normal uses, some electrical equipment often creates internal tiny sparks in switches, motor brushes, connectors, and in other places. A device termed intrinsically safe is designed to not contain any components that produce sparks or which can hold enough energy that could produce a spark.