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1.1 ,This specification covers limestone suitable for use as dust in coal mines to reduce risk of coal dust explosions.
Note 1—,Limestone can serve as a source of incombustible material in coal mine operations. Limestone is dusted onto coal exposures in sufficient amount so that not less than 65 ,% of all loose dust shall be limestone incombustible material. In return air courses the concentration of incombustible materials should be not less than 80 ,% of the total dust (MSHA 30 CFR 75.403). With such a concentration of limestone incombustible material, dust explosions cannot initiate or be propagated from nearby gas explosions. The limestone must be substantially dry in order to dust satisfactorily.