Section 27-368 - Ventilation; condition of airways; testingA. Every underground working place shall have a sufficient amount of ventilation for employees working in such place.B. In any underground working place where there is danger of a serious fire, ventilation shall be controlled by mechanical means.C. The air currents going into underground workings shall have sufficient volume and velocity to direct and carry away smoke and harmful gases from blasting and any other gases or dust which might contaminate the atmosphere.D. Intake and exhaust airways in underground mines shall be maintained in good condition and free from obstruction.E. When the atmosphere in any mine or part of a mine is known to contain or is suspected of containing any explosive or toxic gas, the operator shall test it before employees are allowed to work in such mine or part of such mine.