High-efficiency filter (English: High-Efficiency Particulate Air, or HEPA) is the most popular technology used in air purifiers, and it is also the most stable physical filtration method without side effects. The HEPA filter can absorb 99.7% of 0.3 micron suspended particles (0.3 micron is the most difficult size to filter), making the air sucked fresher and cleaner. Generally, HEPA filters can absorb chemical fumes, bacteria, dust particles and pollen. The advantage of HEPA filter is effective and safe. Its filtering capacity is higher than electrostatic dust collection technology, but it cannot filter out harmful gases.