(a) Air in which men work or travel must promptly be improved if it contains less than 19.5 percent oxygen, more than one percent carbon dioxide, or is contaminated with noxious or poisonous gases.
(b) If the air immediately returning from a split that ventilates any active workings contains more than one percent methane or more, the ventilation shall be improved, and, if it contains 1.5 percent or more of methane, the power shall be cut off from the portion of the mine affected, and the employees shall be required to withdraw until ventilation is improved.
(c) Face work must be stopped, power to face equipment cut off, and the employees ordered and required to withdraw until ventilation is improved, whenever one percent or more of methane can be detected on an approved type methane detector or whenever gas can be detected on a permissible flame safety lamp at any point not less than 12 inches from the roof, face, or rib. This does not apply to other faces in the entry or slope in which work can be safely continued.
(d) When entries or faces are stopped on account of gas for ventilation to be improved, only employees designated to work on improving the ventilation under competent direction may be permitted in the affected area. Power shall not be restored until ventilation is improved.
Last modified: May 3, 2021