A supply of compressed air at a working pressure of about 100 psi (690 kPa). The quantity required for a modern high-speed sinking may be 2,000 to 2,500 ft₃/min (56.6 to 70.7 m₃/min). At a new mine where two shafts are being sunk, the power installation may comprise eight slow-speed water-cooled compressors with a total output of almost 5,000 ft ₃/min (141.5 m₃/min) at 100 psi.