(a) Whenever any equipment or supplies required by this chapter, including rock-dusting machines, flame safety lamps, and permissible electric equipment are unobtainable, compliance with the requirements of this chapter with respect thereto is suspended to the extent that such items remain unobtainable until they are obtainable. Due allowance shall also be made for planning, institution of change procedures, and installation of new equipment.(b) Compliance with the requirements of this chapter shall be started promptly and prosecuted diligently until the provisions of the chapter have been fulfilled.
