30 CFR § 23.14
Instructions for handling future changes in design.
All approvals are granted with the understanding that the manufacturer will make his device according to the drawings that he has submitted to MSHA and that have been considered and included in the approval. Therefore, before making any changes in the design he shall obtain MSHA's authorization of the change. The procedure is as follows:
(a)(1) The manufacturer shall write to the U.S. Department of Labor, Mine Safety and Health Administration, Approval and Certification Center, 765 Technology Drive, Triadelphia, WV 26059, requesting an extension of the original approval and stating the change or changes desired. With this request, the manufacturer should submit a revised drawing or drawings showing the changes in detail, together with one of each of the parts affected.
(2) Where the applicant for approval has used an independent laboratory under part 6 of this chapter to perform, in whole or in part, the necessary testing and evaluation for approval of changes to an approved product under this part, the applicant must provide to MSHA as part of the approval application:
(i) Written evidence of the laboratory's independence and current recognition by a laboratory accrediting organization;
(ii) Complete technical explanation of how the product complies with each requirement in the applicable MSHA product approval requirements;
(iii) Identification of components or features of the product that are critical to the safety of the product; and
(iv) All documentation, including drawings and specifications, as submitted to the independent laboratory by the applicant and as required by this part.