The Best And Worst Face Masks For COVID-19, Ranked by Their Level of Protection

https://www.sciencealert.com/some-masks-are-better-than-others-here-they-are-ranked-best-to-worst

The ideal face mask blocks large respiratory droplets from coughs or sneezes – the primary method by which people pass the coronavirus to others – along with smaller airborne particles, called aerosols, produced when people talk or exhale.

The World Health Organisation recommends medical masks for healthcare workers, elderly people, people with underlying health conditions, and people who have tested positive for the coronavirus or show symptoms. Healthy people who don't fall into these categories should wear a fabric mask, according to WHO.

Over the past few months, scientists have been evaluating the most effective mask materials for trapping the coronavirus. Here are their results so far, from most to least protective....

N95 masks offered better protection than surgical masks.

Disposable surgical masks are a close second, in general, surgical masks are about three times as effective at blocking virus-containing aerosols than homemade face masks.

"Hybrid" masks are the safest homemade option. In a recent paper that hasn't yet been peer-reviewed, researchers in the UK determined that "hybrid" masks – combining two layers of 600-thread-count cotton with another material like silk, chiffon, or flannel – filtered more than 80 percent of small particles (less than 300 nanometres) and more than 90 percent of larger particles (bigger than 300 nanometres).
They found that the combination of cotton and chiffon offered the most protection, followed by cotton and flannel, cotton and silk, and four layers of natural silk.

Three layers of cotton or silk are also highly protective.

WHO recommends that fabric masks have three layers: an inner layer that absorbs, a middle layer that filters, and an outer layer made from a nonabsorbent material like polyester.

Vacuum-cleaner bags are a DIY alternative to surgical masks. The material was almost as good at filtering aerosols as surgical masks, the researchers found.