RT Journal Article SR Electronic T1 Low-cost measurement of face mask efficacy for filtering expelled droplets during speech JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eabd3083 DO 10.1126/sciadv.abd3083 VO 6 IS 36 A1 Fischer, Emma P. A1 Fischer, Martin C. A1 Grass, David A1 Henrion, Isaac A1 Warren, Warren S. A1 Westman, Eric YR 2020 UL http://advances.sciencemag.org/content/6/36/eabd3083.abstract AB Mandates for mask use in public during the recent coronavirus disease 2019 (COVID-19) pandemic, worsened by global shortage of commercial supplies, have led to widespread use of homemade masks and mask alternatives. It is assumed that wearing such masks reduces the likelihood for an infected person to spread the disease, but many of these mask designs have not been tested in practice. We have demonstrated a simple optical measurement method to evaluate the efficacy of masks to reduce the transmission of respiratory droplets during regular speech. In proof-of-principle studies, we compared a variety of commonly available mask types and observed that some mask types approach the performance of standard surgical masks, while some mask alternatives, such as neck gaiters or bandanas, offer very little protection. Our measurement setup is inexpensive and can be built and operated by nonexperts, allowing for rapid evaluation of mask performance during speech, sneezing, or coughing.