NIOSH N95 STANDARD INTRODUCTION:

① N95 standard is one of nine protection level which edited and certificated by NIOSH(National Institute for Occupational Safety and Health) for particulate respirators. 
② Only the respirators/mask meet N95 standard and certified by NIOSH can be called NIOSH N95 mask.
③ "N"means used for against particulate aerosols free of oil.
④ "95"means it filters at least 95% of the particles at aparticle size of 0.3 micron.