Abstract: A protective mask for filtering out and effectively killing harmful organisms includes a transparent or translucent covering for the wearer's mouth. One or more resilient straps hold the covering over the wearer's mouth. Two modules, one at each edge of the covering, are located behind the edge of the eye sockets to reduce the moment of inertia when the wearer turns her head or moves her head up or down. Each module contains two UVC LEDs injecting light into a reflective chamber. A flow rate sensor in the chamber detects a flow rate of inhaled and exhaled air, and a controller supplies current to the LEDs generally proportional to the air flow. To remove heat from the LEDs, the LEDs are thermally coupled to heat sinks, a thermally conductive body of the modules, a thermally conductive grill, a thermally conductive receptacle for the modules, and thermally conductive straps.