Two self-contained, breathing air apparatuses (SCBA) approved by the Bureau of Mines of the United States Department of the interior shall be kept in a suitable cabinet immediately outside the entrance to the machinery room for every system containing over one 1,000 pounds (453.6 kg) of a Group Al refrigerant that operates above atmospheric pressure or over 100 pounds (45.36 kg) of Ammonia (R-717) refrigerant. SCBA equipment shall be rated for at least 30 minutes. When a machinery room is required, at least two approved self-contained breathing apparatus, suitable for the refrigerant used, shall be located outside of, but close to, the machinery room. SCBA equipment shall be fire-resistance rated for at least 30 minutes.