Dr. Ryan Southworth, a board-certified emergency medicine physician and emergency medical services medical director, explains how to make the safest face mask. This is a safe face mask that if built properly should be donated to your local emergency services. It utilizes a HEPA filter, which is much, much better than a cotton mask. HEPA is an OSHA certified filter that can filter out 99.97 percent of airborne particulate matters. A typical N95, on the other hand, does about 95 percent.