20. Where there are fewer than 6 workers, the workers shall be trained in the use of:(1) self-contained breathing apparatus having a minimum utilization time of 60 minutes;
(2) (paragraph revoked);
(3) oxygen therapy apparatus;
(4) gas detectors.
Moreover, at least 3 workers shall be(1) trained in mine rescue as prescribed in section 19 according to the frequency prescribed in the second paragraph of section 18;
(2) available for such training.