Face masks with filters add another layer of protection ...- 3 layer mask with filter pocket for sale online ,Jul 16, 2020·Filters, which are essentially another layer that goes underneath a mask, can either be pre-sewn onto a mask or manually inserted via a pocket. Although the Centers for Disease Control and Prevention currently have no formal recommendations on the use of filters in homemade masks, researchers have tested the efficacy of several commonly found ...$12.95 | Stark's Face Covering | Free Shipping | Buy 4 Get ...Wby I choose your mask in the first place – the vacuum filters. In my homemade mask I place a hepafilter vacuum filter that filters 0.3 micron – not at N95 level but in our need to protect the supply for front line workers it is a great substitute. My husband has difficulty breathing using this type of filtered mask.