About $200 gives you something good enough and easy to operate. From Science Advances
Low-cost measurement of facemask efficacy for filtering expelled droplets during speech
Emma P. Fischer1, Martin C. Fischer2,3,*, David Grass2, Isaac Henrion4, Warren S. Warren2,3,5,6, and Eric Westman7
1Department of Psychology & Neuroscience, Duke University, Durham, NC 27708, USA. 2Department of Chemistry, Duke University, Durham, NC 27708, USA. 3Department of Physics, Duke University, Durham, NC 27708, USA. 4Cover Durham, Durham, NC 27701, USA. 5Department of Radiology, Duke University School of Medicine, Durham, NC 27710, USA. 6Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA. 7Department of Medicine, Duke University School of Medicine, Durham, NC 27708, USA.
Mandates for mask use in public during the recent 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 fleece or bandanas, offer very little protection. Our measurement setup is inexpensive and can be built and operated by non-experts, allowing for rapid evaluation of mask performance during speech, sneezing, or coughing.