I noticed that in a lot of old art, it shows soldiers using scarves, cloths or such to cover their mouths. Sometimes it includes the nose, but not necessarily.
What's the reason for this? Surely cloth doesn't provide nearly enough protection for it to be used as armour.
Could you please help me out with a few images depicting what you're talking about? My suspicion is that you're seeing padded coifs that cover the lower part of the face, or possibly mail coifs that do the same.