The working principle of a vacuum cleaner is as follows: its motor rotates at a high speed and draws in air through the suction inlet, creating a certain level of vacuum in the dust bin. Dust is sucked into the dust filter bag inside the dust bin via the floor brush, extension tubes, handle, flexible hose and main suction pipe, and remains trapped in the bag. The filtered air then passes through a filter sheet before entering the motor—this sheet acts as a protective barrier to prevent dust from being sucked into the motor in case the dust bag ruptures. The air entering the motor flows out with its operation, and an additional filtration step is added before the air exits the vacuum cleaner due to the constant wear of the carbon brushes during motor operation.
The finer the filtration material, the cleaner the air it filters for the vacuum cleaner, but the poorer its air permeability becomes. This impairs the air volume drawn in by the motor and reduces the vacuum cleaner's efficiency. For users, however, a clean and comfortable experience is the primary concern.
Such fine filtration materials have low air permeability, so they are all made into a wavy shape to increase the air-permeable area. Some of these filtration materials can even be washed and reused repeatedly. All filtration materials have a "service life"—meaning the micropores in the material become clogged with fine dust particles after long-term use. Paper dust bags are therefore a relatively ideal option: they are disposable after use, offering both hygiene and convenience. The fibers of fabric dust filter bags become matted after washing, which impairs their filtration and air permeability performance. SMS three-layer composite filtration material is wash-resistant, yet its air permeability is slightly lower.