In this video I go over yet another polypropylene surgical mask with embedded black fibres in the fabric. These fibres are generally not visible to the naked eye and appear after soaking in hydrogen peroxide or rubbing alcohol. I am still not certain what type of particles these are, but they are not from the PP fabric since these fibres sink to the bottom of a water vial. Further investigation needs to be done, but I personally would exercise caution since these fibres can come loose and enter the breathing airways and if they are in fact nanoparticles, they have the opportunity to enter the bloodstream.