How to assure high-quality masks

With artificial, red-coloured saliva, the analysis methods simulate the emission of aerosols, e.g. when coughing or sneezing. Image: Empa

For instance, the "Infection Prevention and Control" expert group of the Science Task Force recently made recommendations regarding quality requirements for community masks. Based on these, Empa has until now tested said community masks during the current crisis. "Within a very short time we have developed and implemented the necessary technologies and processes in our labs," explains René Rossi from Empa's Laboratory for Biomimetic Membranes and Textiles in St. Gallen. In order to avoid the use of hazardous viruses in these experiments, the researchers used artificially stained saliva to simulate what happens in the course of a droplet infection on the inside and outside of a mask. "With the equipment we developed, this situation could be perfectly simulated," says Rossi.

Successful technology transfer: Empa researcher René Rossi can now hand over the analysis procedures and quality standards to TESTEX AG in Zurich. Image: Empa / Philippe Rossier, Ringier

The air permeability (<60 Pa/cm2), splash resistance (impermeable to saliva splashes) and particle filtration efficiency (filtration efficiency of at least 70% for a particle size of 1 micrometer) of textile masks and filter fabrics were investigated. The analysis methods and test protocols for reusable textile community masks are now being transferred to the independent Swiss testing and certification company TESTEX AG in Zurich. Rossi: "We are very satisfied with this successful and extremely fast knowhow and technology transfer."

In addition to the tests for reusability, comfort and harmful substances (STANDARD 100 by OEKO-TEX®), TESTEX was able to launch a label for community masks. According to TESTEX, this label offers consumers orientation in the market for textile masks and the assurance of optimum protection in accordance with the recommendations of the Science Task Force.

Textile community masks. Forster Rohner AG / Schoeller Textil AG

Empa has also already passed on recommendations for local mask production to various textile companies, including the Herisau-based textile finishing company AG Cilander, Forster Rohner AG, Inter-Spitzen AG and Jakob Schlaepfer AG in St. Gallen, and Schoeller Textil AG in Sevelen, which specializes in high-tech fabrics, Flawa in Flawil, Universal Reusable Packaging GmbH in Tägerwilen, Schips AG in Tübach, LTB AG in Liesthal and Nahtlos in St. Gallen. These companies work together in various consortia. Thus, the production of community masks and textile filters with the required properties according to the specifications of the Science Task Force can start immediately. The companies distribute the products via dealers, but also directly.

"Thanks to the agility and innovative strength of Swiss textile companies, coupled with Empa's know-how, and the award of the TESTEX "Community Mask" label, a milestone has been achieved in the development and production of sustainable protective textiles in Switzerland," says Peter Flückiger, Director of Swiss Textiles. According to Flückiger, the industry association is calling on all manufacturers of textile masks to communicate openly what protection requirements they meet.

The use of community masks (left) is – as the name suggests – intended for the general public as a way of minimizing the risk of transmission in particular and thus protecting the environment. The textile masks are primarily aimed at so-called source control, which is intended to prevent the spread of viral material from an infected carrier. It is important to ensure adequate protection against liquid droplets of various sizes, which are produced when coughing or sneezing, and against aerosols (particle size down to 1 micrometer). The masks must allow longer periods of wear and be sufficiently permeable to air to minimize breathing difficulties. Community masks do not fall under the certified standards of surgical masks or FFP 1-3 type respirators. The washable community masks should be reusable.
Surgical masks (pictured right) are designed to prevent larger droplets of pathogens from being secreted by the wearer. They therefore protect the wearer less, as small particles can pass inside and the mask does not fit tightly to the face. On the other hand, they protect the surroundings from virus-containing droplets from an infected wearer.

FFP (filtering face piece) respirators are different: FFP masks (pictured left) are designed to protect the wearer from airborne pollutants and pathogens. Dimensions of the smallest particles that can be caught are in the sub-micrometer range. Surgical masks as well as respiratory masks (type FFP) are currently mostly intended to be worn only once.

Images: Cilander, Unsplash, Istock