During expiration. the carbon dioxide (CO2) levels inside the dead space of a filtering facepiece respirator (FFR) increase significantly above the ambient concentration. To reduce the CO2 concentration inside the dead space. we attach an active lightweight venting system (AVS) comprising a one-way valve. https://www.roamingfreesims.com/product-category/led-pll-direct-to-mains-240v-ac/