(a) The Regulations for Compressed Natural Gas in this chapter apply to the design, installation, and operation of compressed natural gas (CNG) systems and equipment, including those used for compression.     
      (b) If any term, clause, or provision of these rules is for any reason declared invalid, the remainder of the provisions shall remain in full force and effect and shall in no way be affected, impaired, or invalidated.     
      (c) Nothing in these rules shall be construed as requiring, allowing, or approving the unlicensed practice of engineering or any other professional occupation requiring licensure.     
      (d) Unless otherwise stated, the rules in this chapter are not retroactive. Any installation of a CNG system shall meet the requirements of this chapter at the time of installation.     
      (e) This chapter shall not apply to:      
        (1) the production, transportation, storage, sale, or distribution of natural gas that is subject to Commission jurisdiction under Subtitle A or B, Title 3, Texas Utilities Code;       
        (2) pipelines, fixtures, equipment, or facilities to the extent that they are subject to the safety regulations promulgated and enforced by the Railroad Commission of Texas pursuant to Natural Resources Code, Chapter 117, or Subchapter E, Chapter 121, Texas Utilities Code; or       
        (3) the design and installation of any CNG system in ships, barges, sailboats, or other types of watercraft. Such installation is subject to the American Board and Yacht Council (ABYC) and any other applicable standards.       
      (f) This chapter shall not apply to vehicles and fuel supply containers that:      
        (1) are manufactured or installed by original equipment manufacturers; and       
        (2) comply with Title 49, Code of Federal Regulations, the Federal Motor Vehicle Safety Standards.       
      (g) Vehicles and fuel supply containers excluded from the requirements of this chapter pursuant to subsection (f) of this section shall comply with the requirements of §13.24 of this title (relating to School Bus, Public Transportation, Mass Transit, and Special Transit Vehicle Installations and Inspections).     
     Source Note:        The provisions of this §13.1 adopted to be effective November 15, 1990, 15 TexReg 5934; amended to be effective June 1, 1994, 19 TexReg 3168; amended to be effective October 22, 2001, 26 TexReg 8342; amended to be effective July 28, 2003, 28 TexReg 5870; amended to be effective February 15, 2021, 46 TexReg 1035; amended to be effective February 7, 2023, 48 TexReg 507