Neck fleeces, bandanas work poorly as masks, study shows
VANCOUVER A Duke University study of 14 different masks being used to prevent the spread of COVID-19 has found bandanas work poorly and neck fleeces actually make things worse.
The study was published Friday in the American Association for the Advancement of Science online magazine.
It states that while mask use was widespread, and reduced the chance of an infected person spreading the disease, “many of these mask designs have not been tested in practice.”
It noted that due to a global shortage of commercial supplies, there was widespread use of homemade masks and mask alternatives.
In Alberta, numerous municipalities have mandated or are considering mandating masks on transit and in indoor public spaces.
Researchers devised a simple test using a black box, an infrared light and a cellphone to measure the amount of droplets that pass through a particular mask when a person talks.
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 masks, 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 cotton masks.
The knitted masks didn’t 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.