Study measures effectiveness of different face mask materials when coughing

Washington , October 29,2020: The researchers, from the University of Cambridge and Northwestern University, tested the effectiveness of different fabrics at filtering particles between 0.02 and 0.1 micrometres – about the size of most viruses – at high speeds, comparable to coughing or heavy breathing.
The results, reported in the journal BMJ Open, show that most of the fabrics commonly used for non-clinical face masks are effective at filtering ultrafine particles. N95 masks were highly effective, although a reusable HEPA vacuum bag actually exceeded the N95 performance in some respects.
As for homemade masks, those made of multiple layers of fabric were more effective, and those which also incorporated interfacing, which is normally used to stiffen collars, showed a significant improvement in performance. However, this improvement in performance also made them more difficult to breathe through than an N95 mask.
The researchers also studied the performance of different fabrics when damp, and after they had gone through a normal washing and drying cycle. They found that the fabrics worked well while damp and worked sufficiently after one laundry cycle, however, previous studies have shown that repeated washing degrades the fabrics, and the researchers caution that masks should not be reused indefinitely.
“A mask which blocks particles really well but restricts your breathing isn’t an effective mask,” said first author Eugenia O’Kelly from Cambridge’s Department of Engineering.”N95 masks are much easier to breathe through than any fabric combinations with similar levels of filtration”.