83 STAT. ]
PUBLIC LAW 9 M 7 3 - D E C. 30, 1969
771
does not pass over trolley wires or trolley feeder Avires, and if a certified person designated by the operator is continually testing the methane content of the air in such split during mining operations in such workings, it shall be necessary to withdraw all persons, except those referred to i]i section 104(d) of this Act, from the area of the ^"'®' P* limine endangered thereby to a safe area and all electric power shall be cut off from the endangered area only when the air returning from such workings contains 2.0 volume per centum or more of methane. (j) Air Vhich has passed by an opening of any abandoned area shall not be used to Aentilate any working place in the coal mine if such air contains 0.25 A'olume per centum or more of methane. Examinations of such air shall pe made during the pre-shift examination required by subsection (d) of this section. In making such tests, a certified person designated by the operator shall use means approved by the Secretary for detecting methane. P^'or the purposes of this subsection, an area within a panel shall not be deemed to be abandoned until such panel is abandoned. (k) Air that lias passed through an abandoned area or an area which is inaccessible or unsafe for inspection shall not be used to ventilate any working place in any mine. No air which has been used to A entilate an area from which the pillars have been removed shall be used to ventilate any working place in a mine, except that such air, if it does not contain 0.25 volume per centum or more of methane, may he used to ventilate enough advancing working places immediately adjacent to the line of retreat to maintain an orderly sequence of pillar recovery on a set of entries. Methane moni(1) The Secretary or his authorized representative shall require, tor. as an additional device for detecting concentrations of methane, that a methane monitor, approved as reliable by the Secretary after the operative date of this title, be installed, Avhen available, on any electric face cutting equipment, continuous miner, longAvall face equipment, and loading machine, except that no monitor shall be required to be installed on any such equipment prior to the date on which such equipment is required to be permissible under section 305(a) of this title. When installed on any such equipment, such monitor shall be ^°^*' P* ^^^ kept operative and properly maintained and frequently tested as prescribed by the Secretary. The sensing deAnce of such monitor shall be installed as close to the AAorking face as practicable. Such monitor shall be set to deenergize automatically such equipment when such monitor is not operating properly and to give a Avarning automatically Avhen the concentration of methane reaches a maximum percentage determined by an authorized representatiA^e of the Secretary which shall not be more than 1.0 A'olume per centum of methane. An authorized representatiA^e of the Secretary shall require such monitor to deenergize automatically equipment on AV'hich it is installed AA'hen the concentration of methane reaches a maximum percentage determined by such representative A\-hich shall not be more than 2.0 A^olume per centum of methane. (m) Idle and abandoned areas shall be inspected for methane and for oxygen deficiency and other dangerous conditions by a certified person with means approved by the Secretary as soon as possible but not more than three hours before other persons are permitted to enter or work in such areas. Persons, such as pumpmen, Avho are required regularly to enter such areas in the performance of their duties, and Avho are trained and qualified in the use of means approved by the
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