Silicone, or other thermoplastics, have been used for industrial respirators/particulate masks for years. They are a definite improvement over kn95s, in terms of comfort and seal so long as they are properly fit tested. However, prolonged use caused me to develop contact dermatitis, which has not disappeared even though I haven’t used my respirator in over a year and have been prescribed medication. I cleaned/sanitized my respirator before and after each use.