4 ms·

Also N95 have a limited effectiveness over time (e.g. you need to change it regularly).

• dahfizz 5y ago
  This typically applies to surgical masks as well. The reason is that the fibers of the mask have an electrostatic charge. This charge helps the mask filter particles much better, but the charge will wane over time.
  • mindslight 5y ago
    The official guidance on my P100 3M 2297 filters is to replace them when breathing becomes hard or the nuisance organic vapor protection isn't working as well as you'd like. Everything I've found concurs that the particulate filtration does not diminish with time/use.
    • blub 5y ago
      AFAIK some filters are mechanical and others require the electrosatic charge to reach their stated performance. Half-masks or full face masks are typically of the former kind, while smaller masks of the latter kind.
      • mindslight 5y ago
        The 2297 and 2097 filters (at least) are made with electrostatic media. The 2297 touts "Advanced Electret Media" for easier breathing.