  In several countries wearing multiple surgical masks or N95 respirators was
mandatory in public during the COVID pandemic. In this study, we investigated
the transportation and filtering mechanism of heterogeneous nanoparticles and
viruses through surgical masks and N95 respirators. We conducted experiments in
vitro using aerosol spray paints containing nanoparticles and validated the
findings in vivo on a human volunteer. Scanning electron microscopy was
employed to analyse the transportation and distribution of nanoparticles in
different mask layers and on pristine silicon substrates placed on human skin.
We provide analytical insights into the pressure distribution and fluid
velocity profiles within the complex polymer network. Remarkably, our results
showed that both single surgical masks and N95 respirators demonstrated similar
efficiency in filtering colloidal and jet-stream nanoparticles in the air.
These comprehensive findings have significant implications for policymakers in
defining regulations for airborne pandemics and air pollution control.
