For the purpose of this subchapter and subchapter II of this chapter, the term—

((a)) “certified” or “registered” as applied to any person means a person certified or registered by the State in which the coal mine is located to perform duties prescribed by such subchapters, except that, in a State where no program of certification or registration is provided or where the program does not meet at least minimum Federal standards established by the Secretary, such certification or registration shall be by the Secretary;

((b)) “qualified person” means, as the context requires,

((1)) an individual deemed qualified by the Secretary and designated by the operator to make tests and examinations required by this chapter; and

((2)) an individual deemed, in accordance with minimum requirements to be established by the Secretary, qualified by training, education, and experience, to perform electrical work, to maintain electrical equipment, and to conduct examinations and tests of all electrical equipment;

((c)) “permissible” as applied to—

((1)) equipment used in the operation of a coal mine, means equipment, other than permissible electric face equipment, to which an approval plate, label, or other device is attached as authorized by the Secretary and which meets specifications which are prescribed by the Secretary for the construction and maintenance of such equipment and are designed to assure that such equipment will not cause a mine explosion or a mine fire,

((2)) explosives, shot firing units, or blasting devices used in such mine, means explosives, shot firing units, or blasting devices which meet specifications which are prescribed by the Secretary, and

((3)) the manner of use of equipment or explosives, shot firing units, and blasting devices, means the manner of use prescribed by the Secretary;

((d)) “rock dust” means pulverized limestone, dolomite, gypsum, anhydrite, shale, adobe, or other inert material, preferably light colored, 100 per centum of which will pass through a sieve having twenty meshes per linear inch and 70 per centum or more of which will pass through a sieve having two hundred meshes per linear inch; the particles of which when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air; and which does not contain more than 5 per centum of combustible matter or more than a total of 4 per centum of free and combined silica (SiO), or, where the Secretary finds that such silica concentrations are not available, which does not contain more than 5 per centum of free and combined silica;

((e)) “anthracite” means coals with a volatile ratio equal to 0.12 or less;

((f)) “volatile ratio” means volatile matter content divided by the volatile matter plus the fixed carbon;

((g))

((1)) “working face” means any place in a coal mine in which work of extracting coal from its natural deposit in the earth is performed during the mining cycle,

((2)) “working place” means the area of a coal mine inby the last open crosscut,

((3)) “working section” means all areas of the coal mine from the loading point of the section to and including the working faces,

((4)) “active workings” means any place in a coal mine where miners are normally required to work or travel;

((h)) “abandoned areas” means sections, panels, and other areas that are not ventilated and examined in the manner required for working places under ;

((i)) “permissible” as applied to electric face equipment means all electrically operated equipment taken into or used inby the last open crosscut of an entry or a room of any coal mine the electrical parts of which, including, but not limited to, associated electrical equipment, components, and accessories, are designed, constructed, and installed, in accordance with the specifications of the Secretary, to assure that such equipment will not cause a mine explosion or mine fire, and the other features of which are designed and constructed, in accordance with the specifications of the Secretary, to prevent, to the greatest extent possible, other accidents in the use of such equipment; and the regulations of the Secretary or the Director of the United States Bureau of Mines in effect on the operative date of this subchapter relating to the requirements for investigation, testing, approval, certification, and acceptance of such equipment as permissible shall continue in effect until modified or superseded by the Secretary, except that the Secretary shall provide procedures, including, where feasible, testing, approval, certification, and acceptance in the field by an authorized representative of the Secretary, to facilitate compliance by an operator with the requirements of within the periods prescribed therein;

((j)) “low voltage” means up to and including 660 volts; “medium voltage” means voltages from 661 to 1,000 volts; and “high voltage” means more than 1,000 volts;

((k)) Repealed. , , .

((l)) “coal mine” includes areas of adjoining mines connected underground.