Researchers at Johannes Kepler University Linz have now developed a more simple and inexpensive method to accurately test the level of effectiveness when it comes to different types of face masks.

Face masks now come in a wide variety of shapes, colors, and designs. For health and safety reasons, healthcare workers and other system-relevant employees need assurance that face masks meet the current requirements. A penetrometer is a device used to measure aerosol permeability. The device generates aerosol droplets of oily liquids and measures the percentage of droplets passing through the mask.

These devices can be expensive as well as difficult to obtain. As part of an EU project with cooperation partners, researchers at the JKU’s Institute of Biomedical Mechatronics and the Kepler University Hospital have succeeded in developing a more simple, less expensive method that is more openly accessible.

In order to create test aerosol droplets, scientists used a commercially available e-cigarette. E-cigarettes produce droplets that are 300 nanometers in diameter, meaning the droplets are just large enough to be able to pass well through filters and other barriers. The number of aerosol droplets that pass through a material filter sample are studied and then measured. This can be done using either a precision scale or with a light-scattering detector made of simple and inexpensive electronic components.

This light-scattering detector was actually developed and built by a JKU student in the Medical Engineering program for a first-semester project in a course focusing on urinalysis. While developing the detector, the idea came about to also count aerosol droplets in the air.

Just how reliable are these methods? Prof. Werner Baumgartner, head of the institute, explained: "We have tested a wide variety of different kinds of masks, ranging from FFP3 masks to masks made from simple cotton and synthetic fiber cloths. This covers an enormous range of permeability levels from 1-60%, although in contrast to many synthetic fibers, cotton actually protects quite well."

More importantly however, the method developed at the JKU provides results comparable to those generated by more expensive, high-end penetrometers. Prof. Baumgartner added: "Our approach also now allows medical personnel to quickly check for themselves whether or not a new shipment of masks meets the requirements. We can also test to see if the mask is holding up well or if there have been any changes. For example, we found that some masks deteriorate very quickly after they have been worn for a certain time while others last significantly longer."

Bernd Lamprecht, head of the Department of Pulmonary Medicine at the Kepler University Hospital and Vice-Dean at the JKU’s Faculty of Medicine remarked: "As we will continue to see and use face coverings for some time yet, it is extremely important to be able to quickly and reliably check their effectiveness using tests developed on-site. The successful research conducted by Prof. Baumgartner and his team is a prime example of the high level of potential that lies within the collaboration between medicine and mechatronics."

Several examples of using faulty, ineffective face masks and the resulting health risks show that simple, rapid, inexpensive, and widely available filter characterization methods can be tremendously useful, even when the pandemic eventually ceases to be an issue.

A paper describing the method has been published as a pre-print article and submitted to a prestigious journal. The paper is currently under review.

See pre-print version: https://www.preprints.org/manuscript/202012.0486/v1, opens an external URL in a new window