Scientists behind the present study tested numerous modifications to medical procedure masks alongside a range of consumer-grade masks.
Their aim was to determine the masks’ fitted filtration efficiency (FFE), which indicates their effectiveness at blocking particles of similar size to those of SARS-CoV-2.
To achieve this, the researchers used a custom-built exposure chamber at the Environmental Protection Agency’s Human Studies Facility in Chapel Hill, North Carolina.
A particle generator filled the exposure chamber with particles of sodium chloride ranging in size from 0.02–0.60 micrometers (mcm) — slightly smaller than those of SARS-CoV-2, which range from 0.06–0.14 mcm.
Each of the tested masks had a sampling port installed, enabling the scientists to compare sodium chloride concentrations behind the masks against the concentration in the general atmosphere of the exposure chamber.
The researchers instructed an adult male without a beard to wear the masks. As part of the testing, the team asked him to perform a series of movements of his facial muscles, head, and torso, following the recommendations of the Occupational Safety and Health Administration Fit Testing Protocol.
The masks tested included an unmodified medical procedure mask, the same mask with various modifications to improve its fit, and a variety of consumer-grade masks, including cotton and synthetic masks, bandanas, and a neck gaiter covering.
The scientists found that the FFE of the consumer-grade masks ranged from 26.5–79%.
The most effective was a washed two-layer woven nylon mask, while the least effective was a three-layer woven cotton mask.
The unmodified medical procedure mask had an FFE of 38.5%. All of the modifications to the mask improved its FFE. The most effective was wearing a nylon hosiery sleeve over the face mask, increasing FFE to 80.2%, while tying the ear loops and tucking in the mask’s sides increased FFE to 60.3%.
In contrast, an N95 respirator — the gold standard in protection from small particles — had an FFE of 98.4%.
The scientists point out that while modifications to the medical procedure mask significantly improved its FFE, these require a balance with how comfortable they are to wear.
For example, covering the mask in a nylon hosiery sleeve, or applying rubber bands, were both cumbersome and uncomfortable.
For the scientists, their findings demonstrate the potential effectiveness of masks, whether consumer-grade or intended for medical procedures.
As we all know, the masks we've used everyday consumes 8 hours. Nevertheless if it is washable. Yet, we must understood that wearing masks is a must in this pandemic. Based on the aforementioned above, we must be able to know the protective value of the masks so that we can assure our safetiness.