dhl ship5 layer activate carbon filter shipping white blue anti dust protective fadustproof pm2.5 fasafety changable pads for

white blue anti dust protective fadustproof pm2.5 fasafety changable pads for a.1.the first layer: high efficient filter cloth filter the dust of micron.2.the second layer: meltblown cloth to filter industrial pollutants, automobile exhaust, second-hand smoke pollen allergies.3.the third layer: high efficient filter cloth filter benzene and a smaller function of filtering dust microns.4.the fourth layer: activated carbon cloth filter density, sma.