HEPA (High-Efficiency Particulate Air) filter masks and replacement filters are widely available from specialized manufacturers and major online retailers. While "HEPA" is a specific standard for air filtration (capturing 99.97% of 0.3-micron particles), in the context of masks, this often refers to inserts or specialized respirators. Top Places to Buy HEPA Masks & Filters What is a HEPA filter? | US EPA