HONGZHESHEN Breathing Mask City Cycling Mask Sports Face Mask Workout Mask Mouth-Muffle Dust Mask Cycling Masks (Black)

The exhale "valves" don't actually contain a valve. Mine only came with a mesh/fabric disc inside the "valve". That means air will pass through it in both directions. Since the valve passes through the white filter material, that makes the filter useless. Inhaling draws air in through the valve (path of least resistance), bypassing the filter.