A cleaning apparatus may include a flow source such as a fan which creates air flow through a ventilation duct or other structure to be cleaned. A projectile source projects projectiles such as dry ice pellets proximate the structure to dislodge debris particles therefrom and introduce the dislodged debris particles into the air flow. An electrostatic precipitator removes the particles from the air flow. An upstream sensor may be used to detect the particles upstream of the electrostatic precipitator and determine if the structure is clean using a controller. A downstream sensor may be used to detect the particles downstream of the electrostatic precipitator and determine the efficiency of the electrostatic precipitator using the controller. Carbon dioxide within the air flow may also be detected.