3M Mask Exhaust Filter Adapter

thingiverse

The World Health Organization recommends wearing a cloth mask to reduce exhalation of droplets and lower the chance of spreading COVID-19. Half-mask respirators have inlet and outlet valves (see the white and pale blue discs in the inside-the-mask picture) that pass incoming air through the filter while bypassing warm, moist exhalation past the filters. As a result, exhalation is not filtered by these devices. For COVID-19 prevention, an exhaust filter should be added to stop transmitting any (asymptomatic) infection from person to person. The initial exhaust filter is a simple fabric tube held in place with hair bands, rubber bands, tape, or other materials. The exhaust pressure is very low. Outlet filter choice depends on available materials and personal preference. Any shape (bag, circle, triangle, or a thickly-woven sock) will work. I used a gray fabric tube as the outlet filter, which has a visual effect similar to an elephant's trunk. Dimensions for this modification were obtained from my 3M mask using calipers. Perhaps there are CAD models available online. This is an early version of the modification, but it works quite well (even with one broken latch) because it's pressed onto a molded silicone piece. It could likely be smaller or thinner; I aimed for rugged and minimal flow restriction. My preferred contribution to this project is printing an extra for someone else with the same type of mask or adapting it to another model, which can help save lives. Thanks, and stay safe!