Each room or space where an operator is in attendance shall be provided with adequate approved fire-extinguishing appliances conveniently located and conspicuously marked. Any such appliances which have not been approved by Underwriters' Laboratories for use on live parts should be plainly and conspicuously marked with a warning to that effect whenever placed in rooms containing exposed live parts over 300 volts to ground.
34 Pa. Code § 39.90
This section cited in 34 Pa. Code § 39.81 (relating to applicability); 34 Pa. Code § 39.82 (relating to scope); 34 Pa. Code § 39.83 (relating to modification or waiver of provisions); and 34 Pa. Code § 39.192 (relating to scope).