(b) Return air. -- In all mines, electric haulage locomotives operated from trolley wire and other electrical equipment or devices which may ignite gas shall not be used in return air, unless permission is granted by the director for a specified area. For the purpose of this provision, air used to ventilate a section of a mine shall not be considered return air until such time as the air has ventilated all of the workings in the section.
(c) Qualified person to operate cutting machine. -- No person shall be placed in charge of a coal-cutting machine in any mine who is not a qualified person, capable of determining the safety of the roof and sides of the working places and of detecting the presence of explosive gas, unless they are accompanied by a certified or qualified person who has passed such an examination.
(d) Inspections. -- In any mine no machine shall be brought inby the last breakthrough next to the working face until the machine man shall have made an inspection for gas in the place where the machine is to work. If explosive gas in excess of one percent is found in the place, the machine shall not be taken in until the danger is removed.
(e) Indication of gas. -- In working places a suitable approved apparatus for the detection of explosive gas, shall be provided for use with each mining machine when working, and should any indication of explosive gas in excess of one percent appear on any apparatus used for the detection of explosive gas, the person in charge shall immediately stop the machine, cut off the current at the nearest switch and report the condition to the mine foreman or supervisor. The machine shall not again be started in such place until the condition found has been corrected and been pronounced safe by a certified person.
(f) Periodic gas examinations. -- No electric equipment shall be operated in a mine for a longer period than twenty minutes without an examination as above described being made for gas; and if gas is found in excess of one percent, the current shall at once be switched off the machine, and the trailing cable shall forthwith be disconnected from the power supply until the place is pronounced safe.
(g) Operation of mining machines. -- Machine runners and helpers shall use care while operating mining machines. They shall examine the roof of the working place to see that it is safe before starting to operate the machine. They shall not move the machine while the cutter chain is in motion.