A Low-Cost, Real-Time Method to Estimate PPE Mask Leakage Rates

Easily Quantify Leakage and Fit-Test Masks

At a Glance

Researchers at Colorado State University have developed a sensor that is able to determine the leakage rates of respirators or masks during inhalation and exhalation. This sensor allows for rapid leakage testing for the public and workers where conventional fit testing may not be feasible. This test utilizes a lightweight, compact sensor to then calculate the leakage rate through the mask or respirator.


Particle filtering masks, filtering masks, respirators, and other face coverings are commonly used to reduce the intake of aerosols. A mask/respirator must achieve a sufficient level of fit, filtration, and breathability and be worn appropriately to provide adequate protection. Mask leakage, or the fraction of air bypassing the filtering piece, is especially problematic because leakage often depends on individual-level factors such as facial shape, donning procedure, and behavior.

Current methods to quantify mask leakage (i.e., “fit-testing”) are limited in that they test inhalation leakage only, result in the mask being irreversibly altered, and require expensive equipment and trained technicians. These limitations make fit testing impractical for members of the public and for workers outside of traditional workplace respiratory protection programs, as was often the case during the COVID-19 pandemic.


Our researchers aimed to construct a practical and non-intrusive approach for quantifying airflow leakage around the periphery of a mask or respirator when worn. This will provide a reliable method of estimating mask leakage for populations and situations where conventional fit testing is unavailable or impractical.

An individual will often notice some resistance when breathing through a mask or respirator. This resistance results from pressure drop due to drag forces as air flows past fibers in the mask. An estimate of leakage rate can be established by understanding a mask’s pressure drop vs flow relationship and an individual’s breathing rate and volume. A lightweight and compact sensor has been developed that can be attached to the inside surface of a mask to monitor pressure in real-time. The sensor communicates wirelessly via Bluetooth technology, meaning data is easily accessible without expensive testing equipment. The sensor easily attaches to a mask to quickly and accurately take measurements, without destroying the mask. The sensor calibration and pressure change data is output to a mobile application that can be adapted to be accessible for non-trained individuals.

The new approach can provide a clear distinction between well-sealed and leaking, poorly-fit masks and allows rapid leakage testing for both inhalation and exhalation without damaging the mask.


  • Low-cost implementation of fit testing
    • Total testing kit is 1% of currently available, typical testing kit cost
  • Quick testing turnaround and minimal training is needed to perform the test
  • Sensor connects via Bluetooth, allowing for simple data collection
  • Sensitive, with the ability to Identify leaks at rates between approximately minimum of 1% and 15%, and higher depending on the characteristics of the test component and breathing rates
  • Compact and lightweight sensor and testing device
  •  Non-destructive testing
  • Works with any mask or respirator that is not positively pressured
  •  Inhalation rate and exhalation rate are able to be measured
    • May lead to more accurate measurement of leakage rates due to more information


  • Leak and fit testing of masks and respirators for organizations
  • Fit verification testing of masks/respirators
Last Updated: June 2022
Illustration of airflow patterns when wearing a PPE mask

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Christian L’Orange
John Volckens
David H Leith
Casey W Quinn
Jack K Kodros
Bonnie N Young

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Aly Hoeher