29 CFR §1926.100

1. (a)Employees working in areas where there is a possible danger of head injury from impact, or from falling or flying objects, or from electrical shock and burns, shall be protected by protective helmets.
2. (b)Criteria for head protection.
   1. (1)The employer must provide each employee with head protection that meets the specifications contained in any of the following consensus standards:
      1. (i)American National Standards Institute (ANSI) Z89.1-2009, “American National Standard for Industrial Head Protection,” incorporated by reference in § 1926.6;
      2. (ii)American National Standards Institute (ANSI) Z89.1-2003, “American National Standard for Industrial Head Protection,” incorporated by reference in § 1926.6; or
      3. (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 § 1926.6.
   2. (2)The employer must ensure that the head protection provided for each employee exposed to high-voltage electric shock and burns also meets the specifications contained in Section 9.7 (“Electrical Insulation”) of any of the consensus standards identified in paragraph (b)(1) of this section.
   3. (3)OSHA will deem any head protection device that the employer demonstrates is at least as effective as a head protection device constructed in accordance with one of the consensus standards identified in paragraph (b)(1) of this section to be in compliance with the requirements of this section.