The ACS FBS down-draught bench incorporates a ventilated worktop with a G4 grade filter and a secondary HEPA filter to capture particulates. They are clamped into place to prevent contaminant bypass. The inverter (speed) control fan assembly at the base of the bench discharges cleaned air to the rear. The inverter system allows the user to control the rate of suction and regulates the power consumption in line with the fan speed.