Section 75.1106-3 - Storage of liquefied and nonliquefied compressed gas cylinders; requirements(a) Liquefied and nonliquefied compressed gas cylinders stored in an underground coal mine shall be:(1) Clearly marked and identified as to their contents in accordance with Department of Transportation regulations.(2) Placed securely in storage areas designated by the operator for such purpose, and where the height of the coalbed permits, in an upright position, preferably in specially designated racks, or otherwise secured against being accidently tipped over.(3) Protected against damage from falling material, contact with power lines and energized electrical equipment, heat from welding, cutting or soldering, and exposure to flammable liquids.(b) Liquefied and nonliquefied compressed gas cylinders shall not be stored or left unattended in any area inby the last open crosscut of an underground coal mine.(c) When not in use, the valves of all liquefied and nonliquefied compressed gas cylinders shall be in the closed position, and all hoses shall be removed from the cylinder.36 FR 22061, Nov. 19, 1971