Duke University North Carolina researchers investigated the effectiveness of 14 masks and face coverings ability to stop droplets that people expel while talking; each covering was tested 10 times by one speaker and 3 of them by four speakers, all of whom were asked to say the phrase “Stay healthy people.”
“We confirmed that when people speak, small droplets get expelled, so disease can be spread by talking, without coughing or sneezing,” Martin Fischer, one of the study authors, an associate research professor at Duke said. “We could also see that some face coverings performed much better than others in blocking expelled particles.”
N95 masks without valves were found to be the most effective at stopping particles from being expelled while talking with just 0.1% of the droplet escaping compared to no masks. Surgical masks came in second with 1% of droplets escaping while talking compared to no mask. Given that these are the type of masks most needed by hospital workers a variety of homemade and other types of common face coverings were also investigated.
Polypropylene/cotton blend materials released 5% of expelled droplets while talking, and most of the pleated cotton masks tested released about 20% of the droplets expelled while talking. Bananas released 50% of the droplets expelled while talking, and knitted masks provide less protection than any of the cotton ones. Fleece neck gaiters were found to be the worse, these actually increased the number of droplets expelled while talking to 110%.
However, it was noted that these results varied, additional studies are required to determine the effectiveness of commonly worn face masks and coverings according to the researchers. Also keep in mind that these masks were tested with mild talking only, the force of which is substantially less than what shouting, breathing hard as when out of breath, clearing your throat, coughing or sneezing would be.
“We attribute this to the fleece, the textile, breaking up those big particles into many little particles. They tend to hang around longer in the air, they can get carried away easier in the air, so this might actually be counter-productive to wear such a mask,” Fischer said in a video released by the university.
“We certainly encourage everyone to wear a mask, but we want to make sure that when you wear a mask and you go to the trouble of making a mask, you make one, or wear one that actually helps not just you, but helps everyone.”
“If everyone wore a mask, we could stop up to 99 per cent of these droplets before they reach someone else,” Westman said. “About half of infections are from people who don’t show symptoms, and often don’t know they’re infected. They can unknowingly spread the virus when they cough, sneeze and just talk.”
This study was inspired when Duke University began working with a local non-profit to provide free masks to those in need, according to a press release. However, Associate Professor Eric Westman wanted to be sure of which masks were most effective as to not provide people with a false sense of security. Thus the team came up with an easy and cost effective way to test common masks using a cardboard box, laser, a lens, and a cell phone camera to create an inexpensive contraption to test the face masks.
“This was just a demonstration — more work is required to investigate variations in masks, speakers, and how people wear them — but it demonstrates that this sort of test could easily be conducted by businesses and others that are providing masks to their employees or patrons,” said Fischer.
Westman was planning on purchasing some of the masks tested, but said that he did not because this study showed that they would not have been effective at reducing the spread of COVID-19 at all.
“They were no good,” Westman said. “The notion that ‘anything is better than nothing’ didn’t hold true.”
