1. Filter Performance of N99 and N95 Facepiece Respirators Against Viruses and Ultrafine Particles
2. CDC - NPPTL - NIOSH-Approved Particulate Filtering Facepiece Respirators [Internet]. 2020 [cited 2020 May 29]. Available from: https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/default.html
3. Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes. Technical Bulletin. Revision 4. [Internet]. 3M; 2020. Available from: https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf
4. Ancillary Respirator Information, Healthcare FAQs | NPPTL | NIOSH | CDC [Internet]. 2020 [cited 2020 Jul 14]. Available from: https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/respsource3healthcare.html
5. Shortage of personal protective equipment endangering health workers worldwide [Internet]. World Health Organization. [cited 2020 Jun 27]. Available from: https://www.who.int/news-room/detail/03-03-2020-shortage-of-personal-protective-equipment-endangering-health-workers-worldwide