UNIAIR SH2550V with valve is NIOSH Approved N95 masks for at least 95 percent filtration efficiency against certain non-oil based particles such as those from Grinding, Sanding, Sweeping, Sewing, Bagging, or Processing Minerals, Coal, Iron, Ore, Flour, Metal, Wood, and certain other substances. Different from most of the N95 masks, its’ patented buckle allows adjusting the length of the head strap for various facial sizes. Continuous loop design can allow to hang the mask around the neck when not in use. No metal used is suitable for those environments where metal is not allowed. Meet NIOSH 95 and GB2626-2006 standards both. Got China LA approval to use as personal protection equipment for workers.