The post-filter is folded multiple times to create a dense composite structure that allows efficient filtering. The vacuum cleaner uses a multi-stage filtration system that can trap particles as small as 0.3 μm, with an overall filtration efficiency of 99.9%. The addition of pre-filters allows for the initial capture of larger dust particles, effectively reducing the filter pressure. The filter set can be washed and reused after drying, making it easy to clean, economical, and environmentally friendly.