SEBO C Series 3-Step Filtration System: First, the three-layer full size filter(a) collects the vast majority of the debris. Then, the remainder of the particles are collected by the hospital-grade microfilter (b). Finally,the micro-exhaust filter (c) cleans the exhaust air that the vacuum emits. The air belt (d) disperses the filtered exhaust air around the canister which provides a gentle air flow and reduces machine noise. The S-Class filtration system* as described above, results in 99.9% effectiveness to 0.3 microns making the SEBO air belt C vacuums the perfect choice for customers with allergies and asthma. A charcoal microfilter is available to aid in the removal of odors.