• Record Type:
    OSHA Instruction
  • Current Directive Number:
    STD 01-01-001
  • Old Directive Number:
    STD 1-1.1
  • Title:
    Defining the Term "Nominal Diameter"
  • Information Date:

OSHA Instruction STD 1-1.1 October 30, 1978

March 23, 1972


To: National and Field Offices

Subject: Defining the Term "Nominal Diameter"

1. Purpose. To clarify the use of the term "nominal diameter" in Section 1910.23(e)(3)(ii), and to direct answers to inquiries.

2. Background. This requirement establishes the size of pipe acceptable for use in the construction of guard rails. Numerous requests for clarification have been received, principally from employers and field staff.

3. Interpretation. The term "Nominal Diameter" when used to describe the size (diameter) of pipe used in construction of standard railings and posts means the outside diameter. The requirements that pipe railings and posts shall be at least one and one-half inches nominal diameter means that the outside diameter of such shall be not less than one and one-half inches.

4. Effective Date. This instruction is effective immediately, and will remain in effect until canceled or superseded.


Director, of Program Operations


National Office Field

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(Originator: OCSDG)