To limit the probability that combustible dust accumulations and dusts in suspension will reach unsafe concentrations or quantities in the building, which could lead to a fire or explosion in the presence of an ignition source, which could lead to harm to persons.
To limit the probability that combustible dust will return into the atmosphere of the building, which could lead to an ignitable or hazardous accumulation of dust, which could lead to a fire or explosion, which could lead to harm to persons.