Electrical Hazard Signage Affixed to a Protective Fence at an Electrical Substation

Since the early 1900s–1920s, the Electrical Hazard symbol has been used in the electrical and railway industries of England, Germany, and the United States, with early variants featuring lightning bolts and skulls, along with words such as “Danger,” “Hazard,” and “Achtung” as warnings of the Risk of Fatality.

The first standardization was established in IEC 60417:1975 (5036, Dangerous Voltage) for the inclined black lightning-bolt symbol, and later in ISO 3864:1984 as a black lightning bolt enclosed within a yellow triangle.

Today, this symbol is formally standardized and maintained in ISO 7010 (W012, Warning: Electricity) and IEC 60417 (6042, Caution, Risk of Electric Shock), and is universally recognized.