After studying a ticklish question during the Covid-19 pandemic, researchers in Scotland say they have cracked the problem of when to dispose of a face mask.
Face masks require frequent rotations to remain effective, but scant attention has been given to whether people change them regularly enough, said Graham Skinner, an engineer at the Scottish company Insignia Technologies.
The company has developed a label that changes colour when it is time to dispose of masks and other personal protective equipment (PPE).
The labels “use a range of smart pigments and inks that can change colour when exposed to CO2 (carbon dioxide),” Skinner told AFP at the company’s laboratory in Motherwell, near Glasgow.
“When the pandemic started and there was confusion about when to throw out a face mask, we decided to use the technology to develop a colour-changing label that could be suitable for application on PPE like face masks and aprons.”
“The label’s time temperature indicator is activated when packs are opened and the label is adhered to PPE such as masks and aprons. It then changes colour to indicate when the end of the recommended time has been reached,” Skinner said.
The labels are yellow to begin with and gradually turn blue as they deteriorate in effectiveness. The colour change process can take four or six hours.
The labels can be used on disposable or reusable masks.
Dr Ignazio Maria Viola, a physicist from the University of Edinburgh’s School of Engineering, said mouth coverings have been highly effective at stopping the spread of the virus, but noted there is scope for “massive innovation”.
“The research since the beginning of the year has shown that the transmission is completely through droplets exhaled from the mouth of the person and actually the face mask can really prevent the dispersion of this,” he told AFP.
“What we have learned this year has for sure changed the way we will design and manufacture face coverings in the future,” he said.
“There’s so much we know now that we didn’t know eight months ago.”
Face masks could be engineered to target specific droplet sizes, he said.
“In the future we will be able to design a mask that filters exactly the droplets that can carry the virus.”
In August, researchers at the University of Edinburgh found that someone without a mask who stood two metres from a coughing person was exposed to 10,000 times more virus droplets than someone who wore a mask half a metre from a coughing person.
Tests found that the number of droplets was more than 1,000 times lower when wearing even a single-layer cotton mask.
“We knew face masks of various materials are effective to a different extent in filtering small droplets,” Viola said.
“However, when we looked specifically at those larger droplets that are thought to be the most dangerous, we discovered that even the simplest handmade single-layer cotton mask is tremendously effective.
“Therefore wearing a face mask can really make a difference.”
by Stuart GRAHAM