Inexpensive, accessible device provides visual proof that masks block droplets

In a proof-of-concept study, researchers report that a simple, low-cost technique provided visual proof that face masks are effective in reducing droplet emissions during normal wear. They found that the best face coverings were N95 masks without valves — the hospital-grade coverings that are used by front-line health care workers. Surgical or polypropylene masks also performed well. Hand-made cotton face coverings provided good coverage, eliminating a substantial amount of the spray from normal speech. But bandanas and neck fleeces such as balaclavas didn’t block the droplets much at all.