Few issues have aroused as much controversy during the coronavirus pandemic as the use of face masks in public.  Some countries mandated their usage early on, despite initial reticence from the WHO, who updated their guidance as new evidence emerged.  Donald Trump has been a long-time skeptic, however, despite an apparent change in view in recent days.

With such a shifting narrative, it’s perhaps understandable that no real guidelines exist on the most effective materials or designs for facemasks, especially outside of the medical-grade masks used in hospitals.  New research from Florida Atlantic University attempts to close this knowledge gap through the use of visualization of emulated coughs and sneezes.

The researchers setup a flow visualization experiment using a laser light sheet and a distilled water/glycerin mixture to generate the synthetic fog that would replicate a cough.  This was propelled from the mouth of a mannequin, with a number of publicly available masks tested that are not of medical-grade quality.  These range from bandana-style masks to homemade masks and non-sterile, cone-style masks that are available in many pharmacies.

Differing protection

The results suggest that both bandana-style masks and loosely folded facemasks stop a degree of the droplets that are emitted when we cough, but well-fitted masks with multiple layers of quilted fabric were most effective.

The simulation also revealed that without covering, coughs were able to travel more than 8 feet, which is some way further than the 6-foot social distancing guidelines in place around the world.  With a bandana, the droplets traveled around 3 feet 7 inches, and with a folded cotton handkerchief, just 1 foot 3 inches.  The best results, however, were with a stitched quilted cotton mask, which reduced transmission to just 2.5 inches.

“In addition to providing an initial indication of the effectiveness of protective equipment, the visuals used in our study can help convey to the general public the rationale behind social-distancing guidelines and recommendations for using facemasks,” the researchers say. “Promoting widespread awareness of effective preventive measures is crucial at this time as we are observing significant spikes in cases of COVID-19 infections in many states, especially Florida.”

Just as important as the finding that masks do appear to help reduce the spread of cough droplets was the finding that droplets travel much further than previously thought.  Indeed, they found some droplets had traveled up to 12 feet within a minute.

These droplets then remained suspended in midair for around 3 minutes.  Together, these cast a degree of doubt on the reliability of social distancing as a primary means of reducing the spread of pathogens.

“We found that although the unobstructed turbulent jets were observed to travel up to 12 feet, a large majority of the ejected droplets fell to the ground by this point,” the researchers explain. “Importantly, both the number and concentration of the droplets will decrease with increasing distance, which is the fundamental rationale behind social-distancing.”

Of course, while there has been much talk about the response to the virus being led by the science, there is sufficient doubt to that claim to result in a degree of suspicion that these new findings will be acted on.