RISK ENVIRONMENT The type and number of masks you need will depend on where you are going, according to Dr. Josh Schiffer, professor at Fred Hutchinson Cancer Research Center. “It is most critical to mask effectively and consistently when in the highest-risk environments for super spreader events,” he said. Schiffer recommends wearing a cloth mask when walking the dog, for example, and upgrading to a KN95, N95 or double mask when going to the office, grocery store or clinic. MATERIAL “If properly worn, all masks are effective,” said Lawrence Gostin, director of the O’Neill Institute for National and Global Health Law at Georgetown University. But the material and fit of a mask can make a bigger difference than the number you wear.