Worried about the efficacy of cloth masks? A new study showed that washing, drying and reusing cloth masks may be effective for up to a year and may not reduce their ability to filter out viral particles.
“It’s good news for sustainability. That cotton mask that you have been washing, drying and reusing? It’s probably still fine, don’t throw it away,” said lead author Marina Vance, Assistant Professor, at the Department of Mechanical Engineering at the University of Colorado Boulder.
For the study, published in the journal Aerosol and Air Quality Research, the team created double-layered squares of cotton, put them through repeated washing and drying (up to 52 times, the equivalent of a weekly wash for a year) and tested them between about every seven cleaning cycles.
While the masks were not testing using real people, instead, they were mounted on one end of a steel funnel through which researchers could control a consistent flow of air and airborne particles, the researchers tested the masks using realistic to real-life conditions, with high humidity levels and temperatures to mimics the impact on the mask from our breathing.
While the cotton fibers started falling apart over time after repeated washing and drying, the researchers found that did not significantly affect the cloth’s filtration efficiency.
The only noticeable change was that inhalation resistance slightly increased, meaning that the mask may feel a bit more difficult to breathe through after some wear and tear.
The study also confirms previous research that layering a cotton mask on top of a surgical mask — properly fit on one’s face — provides more protection than cloth alone.
The team found that the cotton cloth masks filtered out up to 23 per cent of the smallest particle size (0.3 microns) on which the virus can travel. Bandanas filtered even less, at only 9 per cent.
In comparison, surgical masks filtered out between 42-88 per cent of the tiny particles, and cotton masks on top of surgical masks reached close to 40 per cent filtration efficiency. KN95 and N95 masks unsurprisingly performed the best, filtering out 83-99 per cent of these particles.