{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,14]],"date-time":"2026-02-14T10:01:53Z","timestamp":1771063313730,"version":"3.50.1"},"reference-count":40,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2021,2,24]],"date-time":"2021-02-24T00:00:00Z","timestamp":1614124800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004329","name":"Javna Agencija za Raziskovalno Dejavnost RS","doi-asserted-by":"publisher","award":["P1-0099"],"award-info":[{"award-number":["P1-0099"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Javna Agencija za Raziskovalno Dejavnost RS","doi-asserted-by":"publisher","award":["P1-0125"],"award-info":[{"award-number":["P1-0125"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Javna Agencija za Raziskovalno Dejavnost RS","doi-asserted-by":"publisher","award":["P2-0209"],"award-info":[{"award-number":["P2-0209"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004329","name":"Javna Agencija za Raziskovalno Dejavnost RS","doi-asserted-by":"publisher","award":["P2-0076"],"award-info":[{"award-number":["P2-0076"]}],"id":[{"id":"10.13039\/501100004329","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Size- and time-dependent particle removal efficiency (PRE) of different protective respiratory masks were determined using a standard aerosol powder with the size of particles in the range of an uncoated SARS-CoV-2 virus and small respiratory droplets. Number concentration of particles was measured by a scanning mobility particle sizer. Respiratory protective half-masks, surgical masks, and cotton washable masks were tested. The results show high filtration efficiency of FFP2, FFP3, and certified surgical masks for all sizes of tested particles, while protection efficiency of washable masks depends on their constituent fabrics. Measurements showed decreasing PRE of all masks over time due to transmission of nanoparticles through the mask-face interface. On the other hand, the PRE of the fabric is governed by deposition of the aerosols, consequently increasing the PRE.<\/jats:p>","DOI":"10.3390\/s21051567","type":"journal-article","created":{"date-parts":[[2021,2,25]],"date-time":"2021-02-25T02:36:13Z","timestamp":1614220573000},"page":"1567","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1282-1327","authenticated-orcid":false,"given":"Anja","family":"Poga\u010dnik Krajnc","sequence":"first","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0741-0048","authenticated-orcid":false,"given":"Luka","family":"Pirker","sequence":"additional","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5206-141X","authenticated-orcid":false,"given":"Ur\u0161ka","family":"Gradi\u0161ar Centa","sequence":"additional","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6480-9587","authenticated-orcid":false,"given":"Anton","family":"Gradi\u0161ek","sequence":"additional","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5930-2159","authenticated-orcid":false,"given":"Igor B.","family":"Mekjavic","sequence":"additional","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"}]},{"given":"Matej","family":"Godni\u010d","sequence":"additional","affiliation":[{"name":"Novo Mesto General Hospital, \u0160mihelska Cesta 1, 8000 Novo Mesto, Slovenia"}]},{"given":"Metod","family":"\u010ceba\u0161ek","sequence":"additional","affiliation":[{"name":"HYLA d.o.o., Brn\u010di\u010deva Ulica 47, 1231 Ljubljana, Slovenia"}]},{"given":"Tina","family":"Bregant","sequence":"additional","affiliation":[{"name":"CIRIUS, Novi trg 43 a, 1241 Kamnik, Slovenia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8919-1768","authenticated-orcid":false,"given":"Maja","family":"Rem\u0161kar","sequence":"additional","affiliation":[{"name":"Jo\u017eef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia"},{"name":"Faculty of Mathematics and Physics, University of Ljubljana, Jadranska Cesta 19, 1000 Ljubljana, Slovenia"}]}],"member":"1968","published-online":{"date-parts":[[2021,2,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e41","DOI":"10.1056\/NEJMp2006141","article-title":"Critical supply shortages\u2014the need for ventilators and personal protective equipment during the Covid-19 pandemic","volume":"382","author":"Ranney","year":"2020","journal-title":"N. 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