![]() This evidence suggests that current tests for the filtration efficiency of masks probably can't offer appropriate standards for infectious disease prevention, especially while coughing and sneezing. ![]() A recent study reported that standard surgical masks were not able to block SARS-CoV-2 when COVID-19 patients coughed ( 5). A fit test machine has not been designed for testing the filtration efficiency of masks at the air speed velocity of a sneeze or cough (instead is used for identifying leaks and ensuring the proper functioning of a face piece). These tests basically use aerosols of 0.1-3.0 μm latex spheres at a velocity below 0.25 m/s which is much slower than that of a cough or sneeze ( 4). Bacterial filtration efficiency (BFE), viral filtration efficiency (VFE) and 0.1 μm particle filtration efficiency (PFE) tests are well known for the materials used in the construction of medical face masks. Face masks, such as surgical masks could block micro-droplets (>5 μm) and aerosols (<5 μm) to prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals ( 3). Early studies showed that the velocity of a sneeze was about 46.0-50.0 m/s whereas recent studies demonstrated that the initial velocity of the micro-droplets in a sneeze was about 4.5-7.0 m/s ( 1, 2). Coughing and sneezing can produce airflows at high velocities containing countless micro-droplets. SARS-CoV-2 is primarily transmitted between people through respiratory droplets and small particle droplet nuclei (aerosols). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing respiratory infection, has rapidly spread worldwide. Common mask materials can potentially provide protection against respiratory droplet transmission. Conclusion: Centrifugation-based filtration efficiency test not only compensates shortcomings of current tests for masks, but also offers a simple way to explore new mask materials during pandemics. The filtration efficiency was improved by the increased layers of materials. Other materials also blocked 53.2-66.5% of microspheres and 76.4%-87.9% of particles except the 8 layers of gauze which only blocked 36.7% of particles. Results: The 4 layers of silk could block 93.8% of microspheres and 88.9% of starch particles, followed by the gauze mask (78.5% of microspheres and 90.4% of starch particles) and the 2 layers of cotton (74.6% of microspheres and 87.5-89.0% of particles). Materials and Methods: Efficiency of surgical masks, gauze masks, gauze, cotton, silk, linen and tissue paper on blocking micro-droplet sized starch particles (average 8.2 μm) and latex microspheres (0.75 μm) with a velocity of 44.4 m/s created by centrifugation was qualitatively analyzed by using imaging-based analysis. The goal of this study was to establish a method to evaluate the filtration efficiency of mask materials under extreme conditions. However, current filtration efficiency tests can't evaluate masks under sneeze-like pressure. Face masks are believed to protect people from infection by blocking those droplets. Background: Sneezes produce many pathogen-containing micro-droplets with high velocities of 4.5-50.0 m/s.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |