Flow visualization of an N95 respirator with and without an exhalation valve.
Matthew E. Staymates
This work demonstrates the qualitative fluid flow characteristics of a standard N95 respirator with and without an exhalation valve. Schlieren imaging was used to compare an adult male breathing through an N95 mask with and without a valve. Additionally, strategic lighting of fog droplets was used with a mannequin head to visualize the penetration of droplets through both masks. The mannequin exhaled with a realistic flow rate and velocity that matched an adult male. Additionally, the penetration of fog droplets was also visualized with a custom system that seals each respirator onto the end of a flow tube. Results of all these qualitative experiments suggest that N95 respirators with exhalation valves are not appropriate as a source control strategy for reducing the proliferation of infectious diseases that spread via respiratory droplets.