This refers to safety measures, including installations and procedures, followed to prevent ignition of hydrocarbons arising from static electricity, lightning or stray current.
References:
– American Petroleum Institute, 49 CFR 195.405(a), Protection Against Ignitions Arising out of Static Electricity, Lightning and Stray Current, 2003
– D.A. Crowl and J.F. Louvar. Chemical Process Safety. 3rd Edition. Prentice Hall. Boston. MA. 2011.