29 CFR § 1910.135 - Head protection.
(a) General requirements.
(2) The employer shall ensure that a protective helmet designed to reduce electrical shock hazard is worn by each such affected employee when near exposed electrical conductors which could contact the head.
(b) Criteria for head protection.
(1) Head protection must comply with any of the following consensus standards:
(iii) American National Standards Institute (ANSI) Z89.1-1997, “American National Standard for Personnel Protection - Protective Headwear for Industrial Workers - Requirements,” incorporated by reference in § 1910.6.
(2) Head protection devices that the employer demonstrates are at least as effective as head protection devices that are constructed in accordance with one of the above consensus standards will be deemed to be in compliance with the requirements of this section.