Case Study
Abstract
By December 2020 , SARS-CoV-2 had caused the deaths of nearly 1.5 million people worldwide . A common strategy to mitigate spread of the virus is mask wearing . Considerable data demonstrate that masks can create an effective barrier to the respiratory droplets that can carry the virus . However , the effectiveness of consumer masks for this purpose varies , and there are currently no minimum standards that mask manufacturers must meet . Therefore , a need exists for an athome test of mask barrier function . Here , we demonstrate a simple test to compare the function of selected masks using widely available materials and resources .
Introduction
The novel 2019 severe acute respiratory distress syndrome coronavirus 2 ( SARS-CoV-2 ) emerged from Wuhan , China , in December 2019 , and rapidly spread across the globe . The first travel-related cases in the U . S ., for example , were detected in late January 2020 , and there is evidence of community spread as early as February 26 . 1 On March 11 , the World Health Organization ( WHO ) declared COVID-19 a pandemic . Shortly after the WHO declaration , both the WHO and the United States Center for Disease Control and Prevention ( CDC ) began to recommend wearing masks in public settings . As of December 2020 , statewide or regional mask mandates were in effect in 37 U . S . states , and more than 100 other countries have nationwide mask requirements .
Despite widespread masking , there are neither currently no minimum standards for mask manufacturing in the U . S . nor any requirement for mask manufacturers to demonstrate the effectiveness of their products . As a result , numerous masks made with different materials and designs are on the market , and finding one that is most effective as a barrier for containment of respiratory droplets is the responsibility of the consumer . Hence , there is an urgent need for simple , consumer-friendly , at-home tests of barrier function . Several such methods are available already , but have significant limitations . For example , the idea behind the so-called candle test is that an effective mask will prevent one from being able to blow out a candle , but it is not clear if disrupted airflow is a suitable surrogate for droplet escape as that has not been evaluated in a rigorous manner . Other approaches require specialized equipment , such as lasers combined with lenses and sophisticated computer algorithms 4 or bacterial growth medium and incubators . These items may not be readily available outside of wet laboratories .
Herein , we describe a crude , but likely effective do-it-yourself test to compare the barrier function of different masks that may enable a consumer to select the most effective style from their wardrobe . The test is based on the fact that hairspray atomizers produce liquid droplets with diameters in the same range as respiratory droplets . The apparatus can be assembled in minutes from widely available materials . We also provide results from our own tests with a selection of masks of differing material and construction .
Methods and Results
We purchased UV-fluorescent hairspray , a 10 W black light with a 365 nm UV light-emitting diode ( LED ), a selection
by Marissa K . Johnston , BS ; Mitchell R . McGill , PhD
Dept . of Environmental and Occupational Health , Fay W . Boozman College of Public Health , U UAMS , Little Rock , Ark .
Demonstration of a Simple , Do-it-Yourself Test of Mask Barrier Function Using Widely Available Commercial Products of test masks , and dark-colored construction paper (“ target paper ”) from an online retailer . Comparable products are available through multiple online retailers , as well as brick-and-mortar hobby stores . We then modified a long , rectangular cardboard box by cutting slots in the sides to hold the target paper and masks approximately 0.5 ” apart ( Figure 1A ). To ensure the masks were held firmly in place and stretched similar to regular use , we cut flaps along the sides of the box to accommodate the ear loops and pulled the loops tight . Next , we cut a channel in the bottom of the box to allow entry of the top of the hairspray canister . The channel stopped approximately 1.5 ” back from the mask . We chose to leave a space between the canister and mask to minimize artifactual passage of liquid through the mask due to the high pressure of the liquid stream upon exit from the cannister nozzle . This also ensures that liquid droplets can spread out to avoid saturating the mask in one spot , which may reduce barrier effectiveness . To test the barrier function of a mask , the user simply places the mask and target paper in their respective slots , inserts the canister , briefly sprays the paper through the mask , and then views the target paper under the black light . As we have done in our tests , we recommend including a positive control mask ( such as a common surgical mask ) and / or negative control ( such as a thin neck gaiter ) for comparison . If a consumer mask prevents passage of the hairspray as well as the surgical-style mask , then the consumer mask may be at least a somewhat effective barrier .
To demonstrate use of the apparatus , we tested four common types of mask of
282 • The Journal of the Arkansas Medical Society www . ArkMed . org