Section 75.1107-1 - Fire-resistant hydraulic fluids and fire suppression devices on underground equipment(a)(1) Unattended electrically powered equipment used underground which uses hydraulic fluid shall use approved fire-resistant hydraulic fluid.(2) Except as provided in paragraph (a) (3) of this section, within 24 production shift hours after being installed, unattended electrically powered equipment used underground shall be equipped with a fire suppression device which meets the applicable requirements of §§ 75.1107-3 through 75.1107-16 .(3) Unattended enclosed motors, controls, transformers, rectifiers, and other similar noncombustible electrically powered equipment containing no flammable fluid may be protected: (i) By an approved fire suppression device, or(ii) Be located at least 2 feet from coal or other combustible materials, or(iii) Be separated from the coal or combustible materials by a 4-inch-thick masonry firewall or equivalent; and be mounted on a minimum 4-inch-thick noncombustible surface, platform, or equivalent. The electrical cables at such equipment shall conform with the requirements of Part 18 of this chapter (Bureau of Mines Schedule 2G) or be in metal conduit.(b) Attended electrically powered equipment used underground which uses hydraulic fluid shall use approved fire-resistant hydraulic fluid unless such equipment is protected by a fire suppression device which meets the applicable requirements of §§ 75.1107-3 - 75.1107-16 .(c) For purpose of §§ 75.1107-75 .1107-16 the following underground equipment shall be considered attended equipment: (1) Any machine or device regularly operated by a miner assigned to operate such machine or device;(2) Any machine or device which is mounted in the direct line of sight of a jobsite which is located within 500 feet of such machine or device and which jobsite is regularly occupied by a miner assigned to perform job duties at such jobsite during each production shift.(d) Machines and devices described under paragraph (c) of this section must be inspected for fire and the input powerline deenergized when workmen leave the area for more than 30 minutes.37 FR 15301, July 29, 1972