Usually one filter can be used for 30 days, It is recommended to change at any time during flu and heavy pollution periods.
Activated Carbon Dustproof Mask Are you now troubled by dust chemicals, smoke and particles, Do you want to enjoy a free outdoor life? Common mask ? It has no effect. Moving purifying respirator? It is large and burden That's a good reason to buy this Activated Carbon Dustproof Mask. Refused to be a human vacuum cleaner, wear a dust proof ,anti-haze mask. A Must Have for outdoor activity Suitable for dust, anti-vehicle exhaust, anti-pollen allergy, PM2.5, for cycling, hiking, skiing and other outdoor activities.Material: Lycra Size: Free Size,Suitable for 54-60cm Face Perimeter Sport Type: Cycling, fishing ,hiking ,mountaineering, camping, fitness, running, e Gender: Unisex Feature1: Anti-pollution PM 2.5 Feature2: Dust-proof, windproof, breathable Feature3: Lycra fabric, soft and comfortable