However, living tissue such as mucosal membranes harbors these viruses [136]. As with the need for water, humans need to breathe and are, therefore, naturally exposed to all these surfaces. The need for broad-spectrum protection against airborne microbes has been expressed. Three protective measures against airborne spread of viruses have been suggested to ensure the antiviral efficiency of filter materials and lastly, that these materials are not limited to only one type of device or surface [137].