Effectiveness of Various Masks and Materials

by MADYSEN RAUCH - November 21, 2020 - With nearly every piece of news and life centering around the COVID-19 pandemic and its effects, daily routines have been forced to become either abandoned, like events such as going to the mall with friends and going to the movies, or adopted, such as wearing a mask everywhere one goes.

Everyone is sick of Covid, especially students. But with masks being such a significant part of daily life, it's common to question their necessity and effectiveness. In regards to whether masks themselves are effective, it has been proven and demonstrated throughout numerous occurrences that they are key to the prevention of the spread of COVID-19. For a thorough explanation with the inclusion of various studies and professionals in the epidemiological and other related fields, visit this link to the University of California San Francisco's article that dives in depth into the effectiveness and impact of masks. This significance in the prevention of the spread of this pandemic makes masks a necessity, but in lieu of this, the question has come up as to which masks are the most effective.

A study conducted by researchers at Duke University provides one of (if not) the clearest outcomes and datasets demonstrating which levels of effectiveness correlate with different types of masks. For the setup of this experiment, a laser beam is projected vertically into slits of a dark enclosure, with a camera located at the back of the box. Droplets passing through the beam are visible due to their scattering of light, which is recorded by the camera. Then, a speaker is positioned at the front of the box, wearing one of various masks (or none for a control dataset).

Experimental Setup of Laser Beam (right/upper) and Particles Passing Through (lower left) - photo by: MARTIN FISCHER, Duke University.

When the speaker pronounces their assigned single phrase, the camera records the number of droplets passing through the beam, and a computer algorithm is used to count the exact number. In the experiment, 14 common masks or mask alternatives, a piece of mask material, and a professionally fitted N95 mask, in addition to the control trials in which no face covering was applied were tested. For each mask, the procedure was conducted for four different subjects, each time with the camera recording an approximate 40 second time frame. The first 10 seconds were recorded as the baseline, or the general state with no speaking or other event occurring. In the following 10 seconds, the speaker would repeat the phrase, “Stay healthy, people” five times, and the camera would then record an additional 20 seconds of observation of the speaker. This procedure was repeated 10 times for each material/trial.

14 Different Masks and Materials Tested. Photo credit: EMMA FISCHER, Duke University.

After conducting these trials for each material (or lack thereof), a computer algorithm analyzed the videos and recorded the number of droplets in each video. Below, the results of the data are displayed. In chart A, the solid dots that are displayed are the mean and standard deviations of one speaker over their 10 trials for the material/mask. Empty points are also means and standard deviations, but from four different speakers. In chart B, the droplet count over time is displayed, with corresponding colors to chart A, meaning no mask is shown by green, bandana in red, cotton mask in orange, and surgical mask in blue. The blue line representing the surgical mask is not visible in the chart due to the fact that on this scale it is too small of a value to be viewed.

Data Results

Relative droplet counts for each trial were recorded in relation to the control trials (with no covering), so the fractions shown on the Y-axis of chart A are the relative percentages of droplet counts as they relate to no covering. The relative droplets counts of the various materials ranged from rates of .1% (fitted N95) to 110% (neck gaiter). For the control trial (no mask), the five spikes represent the five repetitions of the phrase. The same is seen in the neck gaiter trial (red), but with other trials, the spikes are almost negligible in comparison to the control and neck gaiter trials. The lines corresponding to the cotton and surgical masks are significantly lower than the other trials, and even standing alone are small, demonstrating the fact that they have small rates of droplet dispersal through the covering, thus protecting those around them from exposure to the virus were the speaker to be infected. This lack of exposure to droplets is key to the functioning of a mask, since COVID-19 is known to be spread through these respiratory droplets, and reducing the exposure of those around a person to their respiratory droplets therefore reduces their risk of COVID-19 if the wearer is infected.

In chart A, the various materials of masks are shown and ranked based on their effectiveness. Essentially, these results show that surgical and fitted N95 masks are the most effective (with specifically tight structure and design so as to prevent the escape of particles), and as far as homemade or easily available masks to the general public go, cotton-polypropylene and two-layer polypropylene masks are the most effective. This effectiveness is likely due to the high moisture-wicking property in polypropylene, meaning that it prevents water droplets from passing through the material, making it ideal for mask material. Additionally, this material is comfortable, with a high breathability for fabric, which makes it much easier to wear for extended periods of time.

While the result of no mask being nearly least effective is not surprising, because the droplets which spread the virus have no barrier preventing their spread, the truly least effective covering was a neck gaiter. Although a neck gaiter does provide a covering that prevents large droplets from passing through, its thinness and lack of tightly woven material results in the breaking down of large droplets into smaller droplets, which are then dispersed anyways. Therefore, the droplet count of neck gaiters is greater than that of no mask because the same amount of original droplets are created and dispersed, but more of the larger droplets are broken down and thus create more smaller and overall droplets as a result of the neck gaiter.

In general, with the exclusion of surgical and fitted N95 masks, which should be reserved for medical personnel, materials which are created from polypropylene are most effective, followed by those with cotton or equitable materials with multiple layers, while no mask is ineffective and neck gaiters actually increase the number of droplets spread, making them the worst option as they are less safe than no mask.

Overall, as lives across the globe are impacted by the pandemic, measures to protect ourselves and those around us have become more important than ever. Educating oneself and those around them is the first step to changing a lifestyle, hopefully in ways that can protect the health and safety of many. In this case, understanding what materials are most effective and why can protect and save the lives of many by preventing the spread of COVID-19. Hopefully, with this understanding along with other scientific and ethical advances, people will be better able to protect themselves and those around them from the newly presented dangers of the current pandemic. For information on the study referenced in this article visit this link. For more information on how to choose masks and materials, visit the links located here and here.

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