KN90 masks have some protection against the new coronavirus, but they are not as effective as N95 and KN95 masks. As N95 and KN95 masks are now scarce, not easy to buy and expensive, so you can wear KN90 masks in places with air circulation such as outdoors. But if you consider the protection effect, it is better to use medical surgical masks, medical care masks and industrial particle protection masks N95, KN95, etc. Other cotton gauze masks, sponge masks, activated carbon masks, etc. are made of cotton, gauze and canvas, which are not fine enough and have large gaps and cannot play an effective protective role, so they are not recommended.