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In scientific parlance, “we have demonstrated a simple optical measurement method to evaluate the efficacy of masks to reduce the transmission of respiratory droplets during regular speech. 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.”
The 14 masks tested included a fitted N95 respirator, a valved N95 respirator, surgical masks, several types of cotton mask, a poly/cotton blended mask, a knitted mask, a bandana and a fleece.
Results showed no droplets at all got through the fitted N95 respirator. The surgical mask was the next best. The cotton masks worked to varying degrees, with the valved N95 mask sitting among the best of the cottons masks.
The knitted masks did not fare well, but using a bandana was worse.The neck fleece used as a mask was actually worse than no mask at all because the droplets were broken down by the fleece and actually spread more.
“We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets, which explains the apparent increase in droplet count relative to no mask in that case,” the report stated.
The relatively poor performance of the valved N95 respirator — given the fitted N95 respirator had perfect results — was attributed to the exhalation valve, which opens for strong outward 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,” the report states.
