Filtration Efficiencies of FFP2 and Surgical Masks After Their Regeneration Using Methods Available in Common Households

RICARDO TISCHENDORF, Hans-Joachim Schmid, University of Paderborn, Germany

     Abstract Number: 202
     Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept

Abstract
During the SARS-CoV-2 pandemic, wearing medical masks in public was often prescribed by policy mandates. Thus, both, FFP2 and surgical masks have been frequently used in 2020 and 2021 worldwide, and people regenerated their masks using techniques that can be found at home (by dry thermal treatment within an oven, or by wet soapy water submersion within washing machines). In the last years, the knowledge about the consequences of those treatments for the Filtration Efficiencies (FEs) of FFP2 mask types was acquired. However, studies focusing on the investigation of the surgical masks FEs in the sub-micron size range are still rare. Hence, we characterized and compared the FEs of FFP2 and surgical masks experimentally before and after their regeneration by two household techniques. Both mask types were characterized by means of an uniform and stabilized teat aerosol, allowing a direct comparison of the derived FE values. For reference, FEs were additionally determined after depolarizing the masks by Isopropanol (IPA) soaking, and the mask performances were compared to commercially available cloth masks.

It was shown, that soapy water submersion influences the FEs of all medicinal masks most critically. The corresponding FE values reduce down to the values of IPA soaking, indicating the masks fibers electrostatic charge loss. However, interestingly, most treated FFP2 masks have still higher FEs in comparison to fresh surgical masks and obviously, utilizing regenerated FFP2 masks instead of fresh surgical masks is clearly better from the filtration point of view. This finding is especially relevant since both medical mask types are treated similarly in several policy mandates (e.g. in Germany 2021/22) and the utilization of recycled FFP2 masks instead of fresh surgical masks would be associated with an increased public protection level.