What 29 CFR 1910.135 requires (plain English)
29 CFR 1910.135 requires head protection in general industry wherever there is a potential for injury to the head from falling objects, and a helmet designed to reduce electrical shock wherever a worker may be near exposed electrical conductors that could contact the head. It is the general-industry counterpart to construction's 1926.100, and it is applied together with the PPE hazard assessment in 1910.132.
Protective helmets must meet the American National Standards Institute standard ANSI Z89.1, which classifies helmets by impact type (Type I for top impact, Type II for top and lateral impact) and by electrical class: Class G (general, tested to 2,200 volts), Class E (electrical, tested to 20,000 volts), and Class C (conductive, which provides no electrical protection). The class must match the hazard: a Class C vented helmet is comfortable but must never be used near energized conductors.
The employer selects the helmet type and class from the 1910.132(d) hazard assessment, must generally pay for it, and must ensure it is worn, maintained, and replaced when damaged or after a significant impact. Head protection works alongside 1926.100 in construction and the electrical safe-work-practice standards where shock is the hazard.