With almost all of the states in the USA mandating a mask to be worn to help curb the spread of COVID-19, we wanted to know what masks were most effective. We found a study published Friday, researchers with Duke’s physics department.
We found this study really interesting but couldn’t help but zero in on this part of the study:
In proof-of-principle studies, we compared a variety of commonly available mask types and observed that some mask types approach the performance of standard surgical masks, while some mask alternatives, such as neck fleece (gator) or bandanas, offer very little protection. Our measurement setup is inexpensive and can be built and operated by non-experts, allowing for rapid evaluation of mask performance during speech, sneezing, or coughing.
We noticed that speaking through some masks (particularly the neck fleece/gator) seemed to disperse the largest droplets into a multitude of smaller droplets (see Supplementary Fig. S5), which explains the apparent increase in droplet count relative to no mask in that case. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive. Furthermore, the performance of the valved N95 mask is likely affected by the exhalation valve, which opens for strong outwards airflow. While the valve does not compromise the protection of the wearer, it can decrease protection of persons surrounding the wearer. In comparison, the performance of the fitted, non-valved N95 mask was far superior.