Links for FDA Authorized KN95 masks
Here are two companies that are reputable mask sellers. The two options are the KN95 masks from China (which are FDA authorized) and the KF94 masks from South Korea. The FDA certification is important to assure these masks are protective. While FDA authorized masks may be available on Amazon or eBay, there are a lot of fake masks around so it can be unclear if you are truly getting a certified mask. Be aware there is a KF80 mask as well yet this is not as protective as the KF94 mask. I’ve also included a link to the FDA website regarding masks. Be aware the term respirators refers to these masks.
FDA Authorized KN95 masks
KF94 (Korean) masks
FDA FAQ regarding masks
FDA Fact sheet on masks. A little technical