Testers also found that "even a polyester bandana can be reasonably effective if it is used in layers, according to the release, which adds that it will filter out "40 percent of suspended particles." "In comparison, the N95 mask used by healthcare workers in hospitals can filter 95 percent of particles or greater." "It filters out over 75% of particles," according to the release. "The testing team measures the density of salt aerosol suspended in the air on one side and compared it to the density on the other side after it passes through the material, the release states, describing the process that is similar to the one used when N95 filters are certified to NIOSH standards.Īfter running about 300 tests, the team found that one of the best readily available materials to use in a homemade face covering is four-ply microfiber cloth, which is popular for cleaning and polishing surfaces, according to the release. The testing involves spraying a salt aerosol at a swatch of material, according to the release. The test team started out by testing materials that defense and federal agencies sent in for evaluation but then then broadened out the effort to evaluate materials likely to be found at home that could be used to make face coverings.
The Pentagon's broad guidance has authorized service members to use everything from T-shirts to their issued neck gaiters as face coverings when social distancing is not possible. "If the resistance is too high, airflow will simply bypass the covering and go around the edges." "The challenge is to pick a material that effectively blocks the virus particles from going through the material while not being too hard to breathe through," said Caretti, said in the release.