Abstract: A particulate respirator facepiece has photocatalyst in the airflow path and a light source that illuminates the photocatalyst. Photocatalyst may include titanium oxide, tin oxide and other semiconductor photocatalysts. Strong oxidizers generated by the illuminated photocatalyst kill infectious agents and decompose toxic organic compounds. The particulate respirator facepiece can be used outdoors, illuminated by natural sunlight; indoors, illuminated by ambient lighting, and; in the dark, with the built-in light source. Light emitting diodes (LEDs) or another source of light built in to the particulate respirator facepiece illuminates the photocatalyst. Light conductors may be incorporated to distribute light from the built-in light source over the photocatalyst.