One year of surgical mask testing at the University of Bologna labs: Lessons learned from data analysis

•A multidisciplinary lab was created to test surgical masks due to COVID outbreak.•435 mask prototypes were tested during the emergency according to the EU standard.•Masks were analyzed according to the material and the number of layers.•A control of aerosol droplet size in the bacterial filtration...

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Bibliographic Details
Published in:	Separation and purification technology Vol. 294; p. 121180
Main Authors:	Boi, C., Borsetti, F., Brugo, T.M., Cappelletti, M., De Angelis, M.G., Fedi, S., Di Giacomo, S., Fabiani, T., Foli, G., Garelli, A., Genchi, U., Ghezzi, D., Gualandi, C., Lalli, E., Magnani, M., Maurizzi, A., Mazzi, F., Mehrabi, N., Minelli, M., Montalbano, R., Morelli, L., Nici, S., Onesti, R., Paglianti, A., Papchenko, K., Pappalardo, S., Parisi, N.F., Rapino, S., Reggio, M., Roselli, M., Ruggeri, E., Sabatini, L., Saracino, E., Scarponi, G.E., Serra, L., Signorini, V., Storione, A., Torsello, M., Tugnoli, E., Vargiu, C.M., Vidali, G., Violante, F.S.
Format:	Journal Article
Language:	English
Published:	Netherlands Elsevier B.V 01-08-2022 The Authors. Published by Elsevier B.V
Subjects:	Bacterial filtration Breathability COVID-19 Pandemic spread prevention Surgical masks COVID-19 Bacterial filtration Breathability Pandemic spread prevention Surgical masks
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Summary:	•A multidisciplinary lab was created to test surgical masks due to COVID outbreak.•435 mask prototypes were tested during the emergency according to the EU standard.•Masks were analyzed according to the material and the number of layers.•A control of aerosol droplet size in the bacterial filtration was found critical.•The standard norm protocols are discussed and best practices are provided. The outbreak of SARS-CoV-2 pandemic highlighted the worldwide lack of surgical masks and personal protective equipment, which represent the main defense available against respiratory diseases as COVID-19. At the time, masks shortage was dramatic in Italy, the first European country seriously hit by the pandemic: aiming to address the emergency and to support the Italian industrial reconversion to the production of surgical masks, a multidisciplinary team of the University of Bologna organized a laboratory to test surgical masks according to European regulations. The group, driven by the expertise of chemical engineers, microbiologists, and occupational physicians, set-up the test lines to perform all the functional tests required. The laboratory started its activity on late March 2020, and as of the end of December of the same year 435 surgical mask prototypes were tested, with only 42 masks compliant to the European standard. From the analysis of the materials used, as well as of the production methods, it was found that a compliant surgical mask is most likely composed of three layers, a central meltblown filtration layer and two external spunbond comfort layers. An increase in the material thickness (grammage), or in the number of layers, does not improve the filtration efficiency, but leads to poor breathability, indicating that filtration depends not only on pure size exclusion, but other mechanisms are taking place (driven by electrostatic charge). The study critically reviewed the European standard procedures, identifying the weak aspects; among the others, the control of aerosol droplet size during the bacterial filtration test results to be crucial, since it can change the classification of a mask when its performance lies near to the limiting values of 95 or 98%.
ISSN:	1383-5866 1873-3794
DOI:	10.1016/j.seppur.2022.121180