Section 293.120 - Air safety requirementsAir in which men work or travel in mines shall be improved when:
(1) It contains less than nineteen and five-tenths percent oxygen;(2) It contains more than one-hundredth percent carbon monoxide;(3) It contains more than five-tenths percent carbon dioxide;(4) It contains more than one percent methane; or(5) Is contaminated with dust or with noxious or poisonous gases in excess of accepted limits as established by the director of the division of mine inspection.