The “N” stands for “Not resistant…to..and the evaluation requirements for N95 masks

N95 is one of the filter standards (42CFR84) for respirator type masks
prescribed by the US National Institute for Occupational Safety and
Health (NIOSH) in 1995. It is recommended for serious communicable
diseases such as tuberculosis, SARS, and influenza. The “N” stands for
“Not resistant to oil,” and the evaluation requirements for N95 masks
stricter than for surgical masks and they also have high filtration efficiency.

New-strain influenzas are easily transmitted from person to person because humans have almost no immunity to them, they could create a global pandemic, and could have a major impact on society accompanying a major health hazard. The government has established an action plan to prepare for the occurrence of a new-strain influenza and is proceeding with preparations based on this plan. It is recommended that as part of the national and local government response that medical facilities be stocked with personal protective gear (including N95) to suppress the spread of infection and minimize the damage if a new-strain influenza occurs. (Source: Ministry of Health, Labour and Welfare website) *Following table: NIOSH anti-dust mask grades USA Standard Japanese Standard Test Dust/Test Flow Volume NIOSH Filtration Rate Disposable Replaceable Filtration rate N95 95％ or more DS2 RS2 95.0％ or more NaCl 85L/分 N99 99％ or more – – – N100 99.97％ or more DS3 RS3 99.9％ or more R95 95％ or more – – – Dioctyl phthalate 85L/min R99 99％ or more – – – R100 99.97％ or more – – – P95 95％ or more DL2 RL2 95.0％ or more Dioctyl phthalate 85L/min P99 99％ or more – – – P100 99.97％ or more DL3 RL3 99.9％ or more