Don't use any mask anymore, not for a cold.Actually it's more dangerous to ware those ffp2 masks.In France they found graphene oxide in those masks, don't know about kn95.Wearing all the time those masks is not so good for your immune system.Btw you can caught MRSA infection and when it comes into your lungs, it's over and out.It will be very hard to get rid of it with antibiotics.