The polluted air is sucked into the extractor hood and transported through the extractor arm to the filter unit. Here, the coarse dust particles are collected in the pre-filter mat. Subsequently, the air is lead through the additional filtering mats to the particle filter which traps extremely fine dust particles with an efficiency of more than 99%. Then the filtered air passes through the activated carbon cassette as a last filter stage where the gases and odours will be refined. Then the air is sucked in by the ventilator and recycled to the air in the workshop through the exhaust grid at the back of the unit.