(a) Results of the engine tests shall be used to calculate
ventilation (cubic feet of air per minute) that shall be supplied by positive
air movement when the permissible mobile diesel-powered transportation
equipment is used underground. This quantity shall be stamped on the approval
plate. The quantity so determined shall apply when only one machine is
(b) Determination of the ventilation rate shall be based upon
dilution of the exhaust gas with normal air. The most undesirable and
hazardous condition of engine operation prescribed by MSHA shall be used in
the calculations. The concentration of any of the following individual
constituents in the diluted mixture shall not exceed:
0.25 percent, by volume, of carbon dioxide (CO(sub)2).
0.005 percent, by volume, of carbon monoxide (CO).
0.00125 percent, by volume, of oxides of nitrogen (calculated as equivalent
nitrogen dioxide, NO(sub)2).
The oxygen (O(sub)2) content of the diluted mixture shall be not less than 20
percent, by volume. The maximum quantity of normal air to produce the above
dilution shall be designated the ventilation rate.
NOTE: This ventilation rate will provide a factor of safety for exposure of
persons to air mixtures containing harmful or objectionable gases and for
minor variations in engine performance.