Modifications of the fit and combination of surgical masks and KN95 respirators to increase respiratory protection against SARS-CoV-2. SciELO Preprints, 2021. DOI: 10.1590/SciELOPreprints.2266. Disponível em: https://preprints.scielo.org/index.php/scielo/preprint/view/2266. Acesso em: 17 jun. 2026.