The pm 2.5 carbon filter is composed of 2 layers of non-woven fabric, 2 layers of meltblown cloth and 1 layer of activated carbon cloth. A Multi-layer replacement air filter gives you. The compatible replacement air filter contains activated carbon, which can effectively prevent haze, car exhaust, pollen, and while letting you breathe fresh air. Each filter can be used up to one week for 8-12 hours per day and up to 1 to 2 weeks for occasional use. After the filters will need to be replaced to continue to get the maximum amount of protection. Two filters per package. The filters cannot be washed.