Reference:
Konda, Abhiteja, et al. "Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks." ACS nano (2020).
Mueller, Amy V., Matthew J. Eden, Jessica J. Oakes, Chiara Bellini, and Loretta A. Fernandez. “Quantitative Method for Comparative Assessment of Particle Filtration Efficiency of Fabric Masks as Alternatives to Standard Surgical Masks for PPE.” MedRxiv, May 18, 2020, 2020.04.17.20069567. https://doi.org/10.1101/2020.04.17.20069567.
Mueller, Amy V., Matthew J. Eden, Jessica J. Oakes, Chiara Bellini, and Loretta A. Fernandez. “Quantitative Method for Comparative Assessment of Particle Filtration Efficiency of Fabric Masks as Alternatives to Standard Surgical Masks for PPE.” MedRxiv, May 18, 2020, 2020.04.17.20069567. https://doi.org/10.1101/2020.04.17.20069567.
Experimental Design:
In the first paper, researchers focused on how fit affected N95 and surgical masks.
First, they tightly wrapped N95 masks, surgical masks, and cloth masks at the end of plastic pipes. Then, they made a mist out of salt water and passed it through each pipe, letting it filter through the mask. They measured the amount of salt water particles left on the other side: fewer particles passing through the mask meant it was more protective.
Second, they poked holes in the plastic pipe. These holes mimic a person wearing a mask that doesn’t fit properly. Then, they passed the salt water mist through the pipe again, measuring the amount of particles left on the other end.
The second paper measured the effect that fit had on cloth and surgical masks.
In an empty room, researchers wore surgical masks and different types of cloth masks. They put on the masks without any modifications, and they did not fit very well. Then, they made a mist out of salt water and passed it into the room. As the researchers breathed, the mist naturally filtered through their masks. They compared the amount of salt water particles inside the mask to the number outside.
Next, the researchers cut a section of pantyhose and wore it over the masks. The pantyhose closed any gaps in the mask, creating a good fit. The salt water mist was passed into the room, and the number of particles found inside and outside the mask were measured again.
First, they tightly wrapped N95 masks, surgical masks, and cloth masks at the end of plastic pipes. Then, they made a mist out of salt water and passed it through each pipe, letting it filter through the mask. They measured the amount of salt water particles left on the other side: fewer particles passing through the mask meant it was more protective.
Second, they poked holes in the plastic pipe. These holes mimic a person wearing a mask that doesn’t fit properly. Then, they passed the salt water mist through the pipe again, measuring the amount of particles left on the other end.
The second paper measured the effect that fit had on cloth and surgical masks.
In an empty room, researchers wore surgical masks and different types of cloth masks. They put on the masks without any modifications, and they did not fit very well. Then, they made a mist out of salt water and passed it into the room. As the researchers breathed, the mist naturally filtered through their masks. They compared the amount of salt water particles inside the mask to the number outside.
Next, the researchers cut a section of pantyhose and wore it over the masks. The pantyhose closed any gaps in the mask, creating a good fit. The salt water mist was passed into the room, and the number of particles found inside and outside the mask were measured again.
Results:
A properly fitting mask makes a HUGE difference. For saliva-spray-sized particles:
- A badly fitted surgical mask filters 60% less than a properly fitted one
- A badly fitted N95 mask filters 88% less than a properly fitted one. That’s only 12% and that’s really bad!
- Depending on their material, cloth masks have a wide range of protection levels
- When a good fit, three types of cloth masks (cotton and chiffon, cotton and silk, cotton and flannel) have filtering abilities above 90%.
- With a bad fit, most cloth masks had 60% filtration ability
- With a good fit, some cloth masks’ filtering abilities increased dramatically, reaching a maximum of 85%.
What does this mean?
Mask fit is EXTREMELY important! Fit makes all the difference between a piece of cloth and a properly working mask. In summary, a cloth mask that fits well is better than a N95 mask that doesn’t!
It’s also important to note that not ALL cloth masks offer equal protection. In this study, only three specific types of cloth worked as well as N95 masks.
It’s also important to note that not ALL cloth masks offer equal protection. In this study, only three specific types of cloth worked as well as N95 masks.
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Up Next: What does a good fit look like?
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