According to a study, poorly fitting face masks greatly increase the risk of infection from airborne diseases like COVID-19 as compared to custom-fitted masks.
Researchers at the University of Cincinnati (UC) in the US used CT scans of three different-sized face masks attached to three different-sized dummy heads to assess the gaps between the face and the fabric. The leakage from these spaces was then quantified to calculate the infection risk.
The study, published in the journal Scientific Reports, found that poorly fitting N95 masks can have significant leaks around the face, reducing their efficiency and increasing the risk of infection.
Dr. Rupak Banerjee, a professor in UC’s Department of Mechanical and Materials Engineering pointed out that “many people do not realize that the fit of face masks can vary. There are different face shapes and different sizes of masks.”
“If you do not match them well, you can lead to greater leaks and higher risks of infection,” he said.
The researchers used three different sizes of N95 face masks along with three standard mannequin heads identified as small, medium, and large.
From the CT scans, they were able to develop a 3-D computer-aided design model that showed the gaps between the masks and the face on each subject.
They determined the relative infection risk for each mask on each face by calculating airflow rates through the gaps.
The aerosol transport attributed to leaking out the sides of the masks varied from as little as 30 percent to as much as 95 percent for the worst-fitting masks.
The leaks were most likely near the nose, according to the researchers. They noticed that the gaps were often asymmetrical on the symmetrical dummy faces.
The study found that poorly fitted face masks might increase the risk of infection for the wearer and others around them.
“A lot of people don’t wear masks properly. They keep the nose exposed, which isn’t helpful,” Dr. Banerjee added.
However, knowing that masks often leak around the nose may encourage people to pay greater attention to fit when purchasing and wearing masks, the researchers said.