An electrostatic charging air cleaning device having first and second pre-chargers. The first pre-charger is configured to generate a first corona discharge to electrostatically charge PM in the incoming air stream with a first charge to form a first exiting air stream exiting the first pre-charger. The second pre-charger is configured to generate a second corona discharge to electrostatically charge PM in the incoming air stream with a second charge to form a second exiting air stream exiting the second pre-charger. The device also includes a separator having apertures such that PM in the second exiting air stream passes through the separator to agglomerate with PM in the first exiting air stream to form agglomerated particles. The apertures are sized such that the agglomerated particles are larger than the apertures to preclude the agglomerated particles from reentering the second exiting air stream.