(a) The director shall establish values to be maintained for the minimum quantities of ventilating air where diesel-powered equipment is operated. The purpose of these rules is to ensure that necessary minimum ventilating air quantity is provided where diesel-powered equipment is operated.

(b) The director shall require that each specific model of diesel-powered equipment shall be approved before it is taken underground. Each diesel engine shall have an assigned MSHA approval number securely attached to the engine with the information required by 30 C. F. R. §§7.90 and 7.105, the approval plate shall also specify the minimum ventilating air quantity required by the director for the specific piece of diesel-powered equipment. The minimum ventilating air quantity shall be determined by the director based on the amount of air necessary at all times to maintain the exhaust emissions at levels not exceeding the exposure limits established pursuant to section four hundred six of this article.

(c) The minimum quantities of air in any split where any individual unit of diesel-powered equipment is being operated shall be at least that specified on the approval plate for that equipment. Air quantity measurements to determine compliance with this requirement shall be made at the individual unit of diesel-powered equipment.

(d) The director shall establish the minimum quantities of air required in any split when multiple units are operated. Air quantity measurements to determine compliance with this requirement shall be made at the most downwind unit of diesel-powered equipment that is being operated in that air split.

(e) Minimum quantities of air in any split where any diesel-powered equipment is operated shall not be less than the minimum air quantities established pursuant to subsections (a) and (b) of this section and shall be specified in the mine diesel ventilation plan.