This PM 2.5 activated carbon (also known as activated charcoal) filter blocks up to 95% of airborne particles — everything from germs and dust to chemicals and pollen — thanks to several (5) strong layers, including a high-efficiency filter cloth and an anti-stick cloth. A tighter filter can help prevent inhaling small droplets in the air we breathe. Each filter can last up to 1 month and can be hand-washed as a delicate item. Sold in packs of 5 for 3.99 + HST. Shipped in 24 hours.