Covid-19: Scientists develop low-cost method to test mask effectiveness

Covid-19: Scientists develop low-cost method to test mask effectiveness against viral droplets

Using widely available tools, scientists have developed a simple method to visualise how

effectively different types of masks prevent the spread of droplets that could contain novel

coronavirus particles, an advance which could aid small scale mask producers to optimise

designs, and help community outreach organisations demonstrate proper mask fitting

procedures.

The technique, described in the journal Science Advances, is still in the early stages, and has

so far only been tested in a small group of people, the scientists said.

According to the researchers from Duke University in the US, the preliminary, proof-ofprinciple

findings suggest that professional-grade N95 masks, surgical or polypropylene

masks, and handmade cotton masks may all block much of the droplet-spray produced when

wearers speak.

However, they said bandanas and neck fleeces likely provide little protection, as the scientists

observed that more droplets are expelled through these materials.

They said this is likely because the materials break up larger droplets as they pass through the

material.

In the study, the scientists evaluated the effectiveness of 14 different types of masks and other

frequently substituted face coverings, using a simple approach in which either onemale speaker

or, in some cases, four speakers wore each mask while standing in a dark enclosure.

The speaker then uttered the phrase “stay healthy, people” five times in the direction of a laser

beam, which scattered light from the droplets released during speech, the study noted.

A cell phone camera recorded the droplets and a simple computer algorithm counted them, the

scientists added.

The setup, intentionally designed to be simple and inexpensive, can be replicated by nonexperts,

according to the researchers.

They said the hardware it requires, including laser equipment, is commonly available and can

be purchased for less than USD 200.

While the researchers acknowledge the need for further testing, they suggested based on the

findings that N95 masks without valves blocked droplet spread best, and surgical or

polypropylene masks and handmade cotton face coverings were also effective.

But the early findings suggested that bandanas and neck fleeces do not provide protection.

“Our work was a demonstration of a simple measurement method, not a systematic mask

study,” noted Martin Fischer, the study’s corresponding author.

“More work is required to investigate variations inmasks, speakers, and how people wear them.

We also want to extend our method to other droplet-generating actions, like coughing and

sneezing. Further, we want to explore effects of incorrect placement and moisture saturation,”

Fischer said.

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mask-effectiveness-against-viral-droplets-124234