Humidity in breath makes cotton masks more effective

A NIST study https://www.nist.gov/news-events/news/2021/03/study-indicates-humidity-breath-makes-cotton-masks-more-effective-slowing indicates that the humidity in breath makes cotton masks more effective at slowing the spread of COVID-19. In this video, a swatch of cotton fabric that has been exposed to high humidity typical of a person’s exhaled breath (left) filters out more droplets than a swatch of cotton fabric that has not been exposed to high humidity (right). Credit: NIST