RS 23:486: Minimum rest interval

The minimum rest interval in open air between shifts shall be:

Normal pressure to eighteen pounds per square inch, eighteen pounds to twenty-six pounds, one hour; twenty-six pounds to thirty-three pounds, two hours; thirty-three pounds to thirty-eight pounds, three hours; thirty-eight pounds to forty-three pounds, four hours; forty-three pounds to forty-eight pounds, five hours; forty-eight pounds to fifty pounds, six hours.