Efficient Three-Stage Filtration System: HEPA Air Purifier features a three-stage filtration system. This comprises a pre-filter, a HEPA filter and an activated carbon filter, powerful enough to captures up dust, pollen, smoke, odor, pet dander, filters particles as small as 0.3 microns and air pollution of PM 2.5.Portable and Durable: The air purifier hepa is of compact design, saving a lot of backpack space, simply connect it into the socket and it runs immediately. Excellent internal structure increases abrasion resist, which obviously extends the life of the machine.Ultra Quiet: With the small fan, the smoke purifier works at a decibel as low as 15-20dB when working, reduces noise so you can sleep in a restful indoor environment, not affect your work, sleep or study, suitable for use at night and in small spaces.Energy-Saving: USB power plugging, the small air purifier runs in low power, makes it more energy-saving. The air purifier works low power consumption, it's more affordable to run all day.Active Carbon Replacement Filters:It is recommended to replace it every 3-5 months.