Flow visualization of an N95 respirator with and without an exhalation valve.

Published

November 10, 2020

Author(s)

Matthew Staymates

Abstract

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.

Citation

Physics of Fluids

Pub Type

Journals

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Keywords

COVID-19, fluid flow, flow visualization, mask, face covering, schlieren imaging, N95

Citation

Staymates, M. (2020), Flow visualization of an N95 respirator with and without an exhalation valve., Physics of Fluids, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=931235 (Accessed October 21, 2025)