The U.S. Army's Chemical Biological Center just ran an extensive round of tests that officials say has revealed the best fabric to use for making homemade face coverings for preventing the spread of coronavirus.
The center, which falls under the Combat Capabilities Development Command, began testing materials around the same time that the Pentagon's April 5 announcement allowing service members to make their own face coverings opened up a flood of discussion on social media.
"We knew that claims about masks and face coverings were exploding all over the internet, and we wanted to make sure that any decisions about materials ... will be based on proven science," David Caretti, who leads the effort as the chief of the Center's Chemical Biological Protection & Decontamination Division, said in a recent Army news release.
The center is one of only a handful of agencies that is experienced in performing tests that precisely measure materials' filtration efficiencies in strict accordance with National Institute for Occupational Safety and Health standards, according to the release.
"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. "If the resistance is too high, airflow will simply bypass the covering and go around the edges."
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.
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 testing involves spraying a salt aerosol at a swatch of material, 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.
After 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.
"It filters out over 75% of particles," according to the release. "In comparison, the N95 mask used by healthcare workers in hospitals can filter 95 percent of particles or greater."
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 early April, Army senior leaders said the service is working on a plan to produce and issue some type of face covering that's either black or camouflage. For now, the color of the face masks is up to unit commanders as long soldiers don't use old Operational Camouflage Uniforms, because they have been treated with chemicals to help repel insects and reduce wrinkles.
Matthew Cox can be reached at email@example.com.