27 C.F.R. § 45.22
The appropriate TTB officer may approve methods of operation other than as specified in this part, where he finds that an emergency exists and the proposed variations from the specified requirements are necessary, and the proposed variations:
Variations from requirements granted under this section are conditioned on compliance with the procedures, conditions, and limitations set forth in the approval of the application. Failure to comply in good faith with such procedures, conditions, and limitations shall automatically terminate the authority for such variations and the manufacturer thereupon shall fully comply with the prescribed requirements of regulations from which the variations were authorized. Authority for any variations may be withdrawn whenever in the judgment of the appropriate TTB officer the revenue is jeopardized or the effective administration of this part is hindered by the continuation of such variation. Where a manufacturer desires to employ such variation, the manufacturer must submit a written application to the appropriate TTB officer. The application shall describe the proposed variations and set forth the reasons therefor. Variations shall not be employed until the application has been approved. The manufacturer shall retain, as part of his records, any authorization of the appropriate TTB officer under this section for three years following the close of the calendar year in which the operation under such authorization is concluded.
27 C.F.R. §45.22