Breathability-old not using

Breathability Testing - Breathability and Particle Filtering Efficiency for Uncertified Masks

Breathability, measured as pressure drop, was performed on numerous devices. All devices were tested with a “Perfect seal” (glued around the edges) and by “Practical fit” over a manikin.  These devices have similar construction using 2 layers of fabric and a middle pouch for insertion of disposable filters made from a non-woven matrix described as “nanofiber” or PM2.5. While the inclusion of a non-woven insert might seem a logical way to improve filtration efficiency, in practice the large pressure drops cause both inhaled and exhaled air to take the path of least resistance around the filtration matrix resulting in poor efficiencies. Devices D & E are commercial gaiter-like designs relying solely on size exclusion filtration. Promotional literature for these 2 devices claims bacterial filtrations of greater than 99% determined using the FDA BFE standard test protocol STP0004 specifying a glued seal over the testing apparatus.  “Practical fit” testing on the manikin gave filtration efficiencies of 52% & 26.2%.