The AOS ESP unit utilises the principle of electrostatic precipitation. The dirty exhaust air is drawn onto the mesh pre-filter which traps large grease particles. The remaining finer particles some small as 0.01-micron pass into a strong electrical field (ionising section) where the particulate receives an electrical charge. The charged particulate then passes onto a collector plate section made up of a series of parallel plates. Each alternate plate is charged with the same polarity as the particles repel are grounded, which attract and collect.