When diesel engine not to be operated underground
52An employer shall ensure that no person operates, and no person shall operate, a diesel engine underground when
(a)
one or more employees in the area where the engine is operating are or will be exposed to air contrary to the requirements of section 47, or
(b)
the flow of air in the area where the engine is operating is less than 4.0 m
3/min. per maximum kilowatt power of the engine being operated.