Why should the velocity of air between the plates of an electrostatic precipitator be low?

Electrostatic precipitator precipitates SPM by attracting them towards the plates. SPM stick on the plates. If the velocity of air is to be high, the charge on plates to be increased significantly otherwise SPM would not feel enough force to attract them to the precipitator due to their momentum. That's why tge velocity of air is reduced so as to increase the efficiency of precipitator even in low charge.