Proper homemade masks also effective against Covid spread: Rotterdam researchers

A homemade face mask can work well against the spread of the coronavirus, as long as it is properly made and contains some form of filter material, according to a study by Erasmus MC in Rotterdam. Filter material used in ventilation systems work best, but kitchen paper also makes an effective filter, researcher Gwen Teesing said to Het Parool.

The researchers tested various homemade masks in a so-called particle chamber, with particles the size of SARS-CoV-2 particles, to see how much of the virus homemade masks filter.

"Such a mask, if properly made, sometimes even works better than some medical masks. The filter must meet certain requirements. With the so-called filter class ePM1 85 percent, which indicates how many fine particles the mask filters, you approach the capacity of a FFP2 mask used in healthcare," Teesing said.

The filter material used in ventilation systems is currently only available wholesale, but the researchers think that other businesses will pick it up if there is enough demand. Two layers of cotton with kitchen paper in between also filters well, the researchers found.

A "duckbill" mask, with space in the front, is the most effective shape, according to Teesing. "The duckbill closes better. The shape is also more comfortable to wear because the mask does not press directly against the nose and mouth, but there is still space inside."